diff --git a/beater/beater.go b/beater/beater.go
index 0ace5cbc907..89486168f00 100644
--- a/beater/beater.go
+++ b/beater/beater.go
@@ -35,6 +35,7 @@ import (
 	"github.com/elastic/apm-server/ingest/pipeline"
 	logs "github.com/elastic/apm-server/log"
 	"github.com/elastic/apm-server/publish"
+	"github.com/elastic/apm-server/sampling"
 )
 
 var (
@@ -172,6 +173,14 @@ func (bt *beater) Run(b *beat.Beat) error {
 	}
 	defer publisher.Stop()
 
+	reporter := publisher.Send
+	if !bt.config.Sampling.KeepUnsampled {
+		// The server has been configured to discard unsampled
+		// transactions. Make sure this is done just before calling
+		// the publisher to avoid affecting aggregations.
+		reporter = sampling.NewDiscardUnsampledReporter(reporter)
+	}
+
 	stopped := make(chan struct{})
 	defer close(stopped)
 	ctx, cancelContext := context.WithCancel(context.Background())
@@ -196,7 +205,7 @@ func (bt *beater) Run(b *beat.Beat) error {
 		Config:   bt.config,
 		Logger:   bt.logger,
 		Tracer:   tracer,
-		Reporter: publisher.Send,
+		Reporter: reporter,
 	})
 }
 
diff --git a/beater/config/config.go b/beater/config/config.go
index 48a2ebeb8cd..1f9c30caa5b 100644
--- a/beater/config/config.go
+++ b/beater/config/config.go
@@ -89,6 +89,7 @@ type Config struct {
 	APIKeyConfig        *APIKeyConfig           `config:"api_key"`
 	JaegerConfig        JaegerConfig            `config:"jaeger"`
 	Aggregation         AggregationConfig       `config:"aggregation"`
+	Sampling            SamplingConfig          `config:"sampling"`
 
 	Pipeline string
 }
@@ -141,6 +142,18 @@ func NewConfig(version string, ucfg *common.Config, outputESCfg *common.Config)
 		return nil, err
 	}
 
+	if !c.Sampling.KeepUnsampled && !c.Aggregation.Enabled {
+		// Unsampled transactions should only be dropped
+		// when transaction aggregation is enabled in the
+		// server. This means the aggregations performed
+		// by the APM UI will not have access to a complete
+		// representation of the latency distribution.
+		logger.Warn("" +
+			"apm-server.sampling.keep_unsampled and " +
+			"apm-server.aggregation.enabled are both false, " +
+			"which will lead to incorrect metrics being reported in the APM UI",
+		)
+	}
 	return c, nil
 }
 
@@ -174,5 +187,6 @@ func DefaultConfig(beatVersion string) *Config {
 		APIKeyConfig: defaultAPIKeyConfig(),
 		JaegerConfig: defaultJaeger(),
 		Aggregation:  defaultAggregationConfig(),
+		Sampling:     defaultSamplingConfig(),
 	}
 }
diff --git a/beater/config/config_test.go b/beater/config/config_test.go
index 9418c31f52a..a695521195b 100644
--- a/beater/config/config_test.go
+++ b/beater/config/config_test.go
@@ -210,6 +210,9 @@ func Test_UnpackConfig(t *testing.T) {
 					MaxTransactionGroups:           123,
 					HDRHistogramSignificantFigures: 1,
 				},
+				Sampling: SamplingConfig{
+					KeepUnsampled: true,
+				},
 			},
 		},
 		"merge config with default": {
@@ -239,9 +242,10 @@ func Test_UnpackConfig(t *testing.T) {
 						},
 					},
 				},
-				"jaeger.grpc.enabled": true,
-				"api_key.enabled":     true,
-				"aggregation.enabled": true,
+				"jaeger.grpc.enabled":     true,
+				"api_key.enabled":         true,
+				"aggregation.enabled":     true,
+				"sampling.keep_unsampled": false,
 			},
 			outCfg: &Config{
 				Host:            "localhost:3000",
@@ -316,6 +320,9 @@ func Test_UnpackConfig(t *testing.T) {
 					MaxTransactionGroups:           1000,
 					HDRHistogramSignificantFigures: 2,
 				},
+				Sampling: SamplingConfig{
+					KeepUnsampled: false,
+				},
 			},
 		},
 		"kibana trailing slash": {
diff --git a/beater/config/sampling.go b/beater/config/sampling.go
new file mode 100644
index 00000000000..c415705f0a3
--- /dev/null
+++ b/beater/config/sampling.go
@@ -0,0 +1,33 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package config
+
+// SamplingConfig holds configuration related to sampling.
+type SamplingConfig struct {
+	// KeepUnsampled controls whether unsampled
+	// transactions should be recorded.
+	KeepUnsampled bool `config:"keep_unsampled"`
+}
+
+func defaultSamplingConfig() SamplingConfig {
+	return SamplingConfig{
+		// In a future major release we will set this to
+		// false, and then later remove the option.
+		KeepUnsampled: true,
+	}
+}
diff --git a/beater/test_approved_es_documents/TestDropNonSampledTransactions.approved.json b/beater/test_approved_es_documents/TestDropNonSampledTransactions.approved.json
new file mode 100644
index 00000000000..e221283f97a
--- /dev/null
+++ b/beater/test_approved_es_documents/TestDropNonSampledTransactions.approved.json
@@ -0,0 +1,1003 @@
+{
+    "events": [
+        {
+            "@metadata": {
+                "beat": "apm-test",
+                "pipeline": "apm",
+                "type": "_doc",
+                "version": "8.0.0"
+            },
+            "@timestamp": "2017-05-30T18:53:27.154Z",
+            "agent": {
+                "name": "js-base",
+                "version": "1.3"
+            },
+            "client": {
+                "ip": "8.8.8.8"
+            },
+            "container": {
+                "id": "container-id"
+            },
+            "ecs": {
+                "version": "1.5.0"
+            },
+            "host": {
+                "architecture": "x64",
+                "ip": "127.0.0.1",
+                "os": {
+                    "platform": "darwin"
+                }
+            },
+            "http": {
+                "request": {
+                    "body": {
+                        "original": {
+                            "additional": {
+                                "bar": 123,
+                                "req": "additional information"
+                            },
+                            "str": "hello world"
+                        }
+                    },
+                    "cookies": {
+                        "c1": "v1",
+                        "c2": "v2"
+                    },
+                    "env": {
+                        "GATEWAY_INTERFACE": "CGI/1.1",
+                        "SERVER_SOFTWARE": "nginx"
+                    },
+                    "headers": {
+                        "Array": [
+                            "foo",
+                            "bar",
+                            "baz"
+                        ],
+                        "Content-Type": [
+                            "text/html"
+                        ],
+                        "Cookie": [
+                            "c1=v1,c2=v2"
+                        ],
+                        "Some-Other-Header": [
+                            "foo"
+                        ],
+                        "User-Agent": [
+                            "Mozilla Chrome Edge"
+                        ]
+                    },
+                    "method": "post",
+                    "socket": {
+                        "encrypted": true,
+                        "remote_address": "8.8.8.8"
+                    }
+                },
+                "response": {
+                    "finished": true,
+                    "headers": {
+                        "Content-Type": [
+                            "application/json"
+                        ]
+                    },
+                    "headers_sent": true,
+                    "status_code": 200
+                },
+                "version": "1.1"
+            },
+            "kubernetes": {
+                "namespace": "namespace1",
+                "pod": {
+                    "name": "pod-name",
+                    "uid": "pod-uid"
+                }
+            },
+            "labels": {
+                "bool_error": false,
+                "number_code": 2,
+                "organization_uuid": "9f0e9d64-c185-4d21-a6f4-4673ed561ec8"
+            },
+            "observer": {
+                "ephemeral_id": "00000000-0000-0000-0000-000000000000",
+                "hostname": "",
+                "id": "fbba762a-14dd-412c-b7e9-b79f903eb492",
+                "type": "test-apm-server",
+                "version": "8.0.0",
+                "version_major": 8
+            },
+            "process": {
+                "args": [
+                    "node",
+                    "server.js"
+                ],
+                "pid": 1234,
+                "ppid": 6789,
+                "title": "node"
+            },
+            "processor": {
+                "event": "transaction",
+                "name": "transaction"
+            },
+            "service": {
+                "environment": "staging",
+                "framework": {
+                    "name": "Express",
+                    "version": "1.2.3"
+                },
+                "language": {
+                    "name": "ecmascript",
+                    "version": "8"
+                },
+                "name": "serviceabc",
+                "node": {
+                    "name": "special-name"
+                },
+                "runtime": {
+                    "name": "javascript",
+                    "version": "8.0.0"
+                },
+                "version": "5.1.3"
+            },
+            "source": {
+                "ip": "8.8.8.8"
+            },
+            "timestamp": {
+                "us": 1496170407154000
+            },
+            "trace": {
+                "id": "945254c567a5417eaaaaaaaaaaaaaaaa"
+            },
+            "transaction": {
+                "custom": {
+                    "(": "not a valid regex and that is fine",
+                    "and_objects": {
+                        "foo": [
+                            "bar",
+                            "baz"
+                        ]
+                    },
+                    "my_key": 1,
+                    "some_other_value": "foo bar"
+                },
+                "duration": {
+                    "us": 32592
+                },
+                "id": "945254c567a5417e",
+                "marks": {
+                    "another_mark": {
+                        "some_float": 10,
+                        "some_long": 10
+                    },
+                    "navigationTiming": {
+                        "appBeforeBootstrap": 608.9300000000001,
+                        "navigationStart": -21
+                    }
+                },
+                "name": "GET /api/types",
+                "page": {
+                    "referer": "http://localhost:8000/test/e2e/",
+                    "url": "http://localhost:8000/test/e2e/general-usecase/"
+                },
+                "result": "success",
+                "sampled": true,
+                "span_count": {
+                    "dropped": 2,
+                    "started": 4
+                },
+                "type": "request"
+            },
+            "url": {
+                "domain": "www.example.com",
+                "fragment": "#hash",
+                "full": "https://www.example.com/p/a/t/h?query=string#hash",
+                "original": "/p/a/t/h?query=string#hash",
+                "path": "/p/a/t/h",
+                "port": 8080,
+                "query": "?query=string",
+                "scheme": "https"
+            },
+            "user": {
+                "email": "foo@example.com",
+                "id": "99"
+            },
+            "user_agent": {
+                "original": "Mozilla Chrome Edge"
+            }
+        },
+        {
+            "@metadata": {
+                "beat": "apm-test",
+                "pipeline": "apm",
+                "type": "_doc",
+                "version": "8.0.0"
+            },
+            "@timestamp": "2017-05-30T18:53:27.154Z",
+            "agent": {
+                "name": "elastic-node",
+                "version": "3.14.0"
+            },
+            "container": {
+                "id": "container-id"
+            },
+            "ecs": {
+                "version": "1.5.0"
+            },
+            "host": {
+                "architecture": "x64",
+                "ip": "127.0.0.1",
+                "os": {
+                    "platform": "darwin"
+                }
+            },
+            "kubernetes": {
+                "namespace": "namespace1",
+                "pod": {
+                    "name": "pod-name",
+                    "uid": "pod-uid"
+                }
+            },
+            "labels": {
+                "span_tag": "something"
+            },
+            "observer": {
+                "ephemeral_id": "00000000-0000-0000-0000-000000000000",
+                "hostname": "",
+                "id": "fbba762a-14dd-412c-b7e9-b79f903eb492",
+                "type": "test-apm-server",
+                "version": "8.0.0",
+                "version_major": 8
+            },
+            "parent": {
+                "id": "945254c567a5417e"
+            },
+            "process": {
+                "args": [
+                    "node",
+                    "server.js"
+                ],
+                "pid": 1234,
+                "ppid": 6789,
+                "title": "node"
+            },
+            "processor": {
+                "event": "span",
+                "name": "transaction"
+            },
+            "service": {
+                "environment": "staging",
+                "framework": {
+                    "name": "Express",
+                    "version": "1.2.3"
+                },
+                "language": {
+                    "name": "ecmascript",
+                    "version": "8"
+                },
+                "name": "1234_service-12a3",
+                "node": {
+                    "name": "container-id"
+                },
+                "runtime": {
+                    "name": "node",
+                    "version": "8.0.0"
+                },
+                "version": "5.1.3"
+            },
+            "span": {
+                "action": "query",
+                "db": {
+                    "instance": "customers",
+                    "statement": "SELECT * FROM product_types WHERE user_id=?",
+                    "type": "sql",
+                    "user": {
+                        "name": "readonly_user"
+                    }
+                },
+                "duration": {
+                    "us": 3781
+                },
+                "http": {
+                    "method": "get",
+                    "response": {
+                        "status_code": 200
+                    },
+                    "url": {
+                        "original": "http://localhost:8000"
+                    }
+                },
+                "id": "0aaaaaaaaaaaaaaa",
+                "name": "SELECT FROM product_types",
+                "stacktrace": [
+                    {
+                        "abs_path": "net.js",
+                        "context": {
+                            "post": [
+                                "    ins.currentTransaction = prev",
+                                "    return result",
+                                "}"
+                            ],
+                            "pre": [
+                                "  var trans = this.currentTransaction",
+                                ""
+                            ]
+                        },
+                        "exclude_from_grouping": false,
+                        "filename": "net.js",
+                        "function": "onread",
+                        "library_frame": true,
+                        "line": {
+                            "column": 4,
+                            "context": "line3",
+                            "number": 547
+                        },
+                        "module": "some module",
+                        "vars": {
+                            "key": "value"
+                        }
+                    },
+                    {
+                        "exclude_from_grouping": false,
+                        "filename": "my2file.js",
+                        "line": {
+                            "number": 10
+                        }
+                    }
+                ],
+                "start": {
+                    "us": 2830
+                },
+                "subtype": "postgresql",
+                "sync": false,
+                "type": "db"
+            },
+            "timestamp": {
+                "us": 1496170407154000
+            },
+            "trace": {
+                "id": "945254c567a5417eaaaaaaaaaaaaaaaa"
+            },
+            "transaction": {
+                "id": "945254c567a5417e"
+            },
+            "user": {
+                "email": "foo@bar.com",
+                "id": "123user",
+                "name": "foo"
+            }
+        },
+        {
+            "@metadata": {
+                "beat": "apm-test",
+                "pipeline": "apm",
+                "type": "_doc",
+                "version": "8.0.0"
+            },
+            "@timestamp": "2017-05-30T18:53:27.154Z",
+            "agent": {
+                "name": "elastic-node",
+                "version": "3.14.0"
+            },
+            "container": {
+                "id": "container-id"
+            },
+            "ecs": {
+                "version": "1.5.0"
+            },
+            "host": {
+                "architecture": "x64",
+                "ip": "127.0.0.1",
+                "os": {
+                    "platform": "darwin"
+                }
+            },
+            "kubernetes": {
+                "namespace": "namespace1",
+                "pod": {
+                    "name": "pod-name",
+                    "uid": "pod-uid"
+                }
+            },
+            "observer": {
+                "ephemeral_id": "00000000-0000-0000-0000-000000000000",
+                "hostname": "",
+                "id": "fbba762a-14dd-412c-b7e9-b79f903eb492",
+                "type": "test-apm-server",
+                "version": "8.0.0",
+                "version_major": 8
+            },
+            "parent": {
+                "id": "945254c567a5417e"
+            },
+            "process": {
+                "args": [
+                    "node",
+                    "server.js"
+                ],
+                "pid": 1234,
+                "ppid": 6789,
+                "title": "node"
+            },
+            "processor": {
+                "event": "span",
+                "name": "transaction"
+            },
+            "service": {
+                "environment": "staging",
+                "framework": {
+                    "name": "Express",
+                    "version": "1.2.3"
+                },
+                "language": {
+                    "name": "ecmascript",
+                    "version": "8"
+                },
+                "name": "1234_service-12a3",
+                "node": {
+                    "name": "container-id"
+                },
+                "runtime": {
+                    "name": "node",
+                    "version": "8.0.0"
+                },
+                "version": "5.1.3"
+            },
+            "span": {
+                "duration": {
+                    "us": 32592
+                },
+                "id": "1aaaaaaaaaaaaaaa",
+                "name": "GET /api/types",
+                "start": {
+                    "us": 0
+                },
+                "subtype": "external",
+                "type": "request"
+            },
+            "timestamp": {
+                "us": 1496170407154000
+            },
+            "trace": {
+                "id": "945254c567a5417eaaaaaaaaaaaaaaaa"
+            },
+            "transaction": {
+                "id": "945254c567a5417e"
+            },
+            "user": {
+                "email": "foo@bar.com",
+                "id": "123user",
+                "name": "foo"
+            }
+        },
+        {
+            "@metadata": {
+                "beat": "apm-test",
+                "pipeline": "apm",
+                "type": "_doc",
+                "version": "8.0.0"
+            },
+            "@timestamp": "2017-05-30T18:53:27.154Z",
+            "agent": {
+                "name": "elastic-node",
+                "version": "3.14.0"
+            },
+            "container": {
+                "id": "container-id"
+            },
+            "ecs": {
+                "version": "1.5.0"
+            },
+            "host": {
+                "architecture": "x64",
+                "ip": "127.0.0.1",
+                "os": {
+                    "platform": "darwin"
+                }
+            },
+            "kubernetes": {
+                "namespace": "namespace1",
+                "pod": {
+                    "name": "pod-name",
+                    "uid": "pod-uid"
+                }
+            },
+            "observer": {
+                "ephemeral_id": "00000000-0000-0000-0000-000000000000",
+                "hostname": "",
+                "id": "fbba762a-14dd-412c-b7e9-b79f903eb492",
+                "type": "test-apm-server",
+                "version": "8.0.0",
+                "version_major": 8
+            },
+            "parent": {
+                "id": "945254c567a5417e"
+            },
+            "process": {
+                "args": [
+                    "node",
+                    "server.js"
+                ],
+                "pid": 1234,
+                "ppid": 6789,
+                "title": "node"
+            },
+            "processor": {
+                "event": "span",
+                "name": "transaction"
+            },
+            "service": {
+                "environment": "staging",
+                "framework": {
+                    "name": "Express",
+                    "version": "1.2.3"
+                },
+                "language": {
+                    "name": "ecmascript",
+                    "version": "8"
+                },
+                "name": "1234_service-12a3",
+                "node": {
+                    "name": "container-id"
+                },
+                "runtime": {
+                    "name": "node",
+                    "version": "8.0.0"
+                },
+                "version": "5.1.3"
+            },
+            "span": {
+                "action": "post",
+                "duration": {
+                    "us": 3564
+                },
+                "id": "2aaaaaaaaaaaaaaa",
+                "name": "GET /api/types",
+                "start": {
+                    "us": 1845
+                },
+                "subtype": "http",
+                "type": "request"
+            },
+            "timestamp": {
+                "us": 1496170407154000
+            },
+            "trace": {
+                "id": "945254c567a5417eaaaaaaaaaaaaaaaa"
+            },
+            "transaction": {
+                "id": "945254c567a5417e"
+            },
+            "user": {
+                "email": "foo@bar.com",
+                "id": "123user",
+                "name": "foo"
+            }
+        },
+        {
+            "@metadata": {
+                "beat": "apm-test",
+                "pipeline": "apm",
+                "type": "_doc",
+                "version": "8.0.0"
+            },
+            "@timestamp": "2017-05-30T18:53:27.154Z",
+            "agent": {
+                "name": "elastic-node",
+                "version": "3.14.0"
+            },
+            "child": {
+                "id": [
+                    "4aaaaaaaaaaaaaaa"
+                ]
+            },
+            "container": {
+                "id": "container-id"
+            },
+            "ecs": {
+                "version": "1.5.0"
+            },
+            "host": {
+                "architecture": "x64",
+                "ip": "127.0.0.1",
+                "os": {
+                    "platform": "darwin"
+                }
+            },
+            "kubernetes": {
+                "namespace": "namespace1",
+                "pod": {
+                    "name": "pod-name",
+                    "uid": "pod-uid"
+                }
+            },
+            "observer": {
+                "ephemeral_id": "00000000-0000-0000-0000-000000000000",
+                "hostname": "",
+                "id": "fbba762a-14dd-412c-b7e9-b79f903eb492",
+                "type": "test-apm-server",
+                "version": "8.0.0",
+                "version_major": 8
+            },
+            "parent": {
+                "id": "945254c567a5417e"
+            },
+            "process": {
+                "args": [
+                    "node",
+                    "server.js"
+                ],
+                "pid": 1234,
+                "ppid": 6789,
+                "title": "node"
+            },
+            "processor": {
+                "event": "span",
+                "name": "transaction"
+            },
+            "service": {
+                "environment": "staging",
+                "framework": {
+                    "name": "Express",
+                    "version": "1.2.3"
+                },
+                "language": {
+                    "name": "ecmascript",
+                    "version": "8"
+                },
+                "name": "1234_service-12a3",
+                "node": {
+                    "name": "container-id"
+                },
+                "runtime": {
+                    "name": "node",
+                    "version": "8.0.0"
+                },
+                "version": "5.1.3"
+            },
+            "span": {
+                "duration": {
+                    "us": 13980
+                },
+                "id": "3aaaaaaaaaaaaaaa",
+                "name": "GET /api/types",
+                "start": {
+                    "us": 0
+                },
+                "type": "request"
+            },
+            "timestamp": {
+                "us": 1496170407154000
+            },
+            "trace": {
+                "id": "945254c567a5417eaaaaaaaaaaaaaaaa"
+            },
+            "transaction": {
+                "id": "945254c567a5417e"
+            },
+            "user": {
+                "email": "foo@bar.com",
+                "id": "123user",
+                "name": "foo"
+            }
+        },
+        {
+            "@metadata": {
+                "beat": "apm-test",
+                "pipeline": "apm",
+                "type": "_doc",
+                "version": "8.0.0"
+            },
+            "@timestamp": "2017-05-30T18:53:42.281Z",
+            "agent": {
+                "name": "elastic-node",
+                "version": "3.14.0"
+            },
+            "container": {
+                "id": "container-id"
+            },
+            "ecs": {
+                "version": "1.5.0"
+            },
+            "host": {
+                "architecture": "x64",
+                "ip": "127.0.0.1",
+                "os": {
+                    "platform": "darwin"
+                }
+            },
+            "kubernetes": {
+                "namespace": "namespace1",
+                "pod": {
+                    "name": "pod-name",
+                    "uid": "pod-uid"
+                }
+            },
+            "observer": {
+                "ephemeral_id": "00000000-0000-0000-0000-000000000000",
+                "hostname": "",
+                "id": "fbba762a-14dd-412c-b7e9-b79f903eb492",
+                "type": "test-apm-server",
+                "version": "8.0.0",
+                "version_major": 8
+            },
+            "process": {
+                "args": [
+                    "node",
+                    "server.js"
+                ],
+                "pid": 1234,
+                "ppid": 6789,
+                "title": "node"
+            },
+            "processor": {
+                "event": "transaction",
+                "name": "transaction"
+            },
+            "service": {
+                "environment": "staging",
+                "framework": {
+                    "name": "Express",
+                    "version": "1.2.3"
+                },
+                "language": {
+                    "name": "ecmascript",
+                    "version": "8"
+                },
+                "name": "1234_service-12a3",
+                "node": {
+                    "name": "container-id"
+                },
+                "runtime": {
+                    "name": "node",
+                    "version": "8.0.0"
+                },
+                "version": "5.1.3"
+            },
+            "timestamp": {
+                "us": 1496170422281000
+            },
+            "trace": {
+                "id": "85925e55b43f4340aaaaaaaaaaaaaaaa"
+            },
+            "transaction": {
+                "duration": {
+                    "us": 13980
+                },
+                "id": "85925e55b43f4340",
+                "name": "GET /api/types",
+                "result": "failure",
+                "sampled": true,
+                "span_count": {
+                    "started": 0
+                },
+                "type": "request"
+            },
+            "user": {
+                "email": "foo@bar.com",
+                "id": "123user",
+                "name": "foo"
+            }
+        },
+        {
+            "@metadata": {
+                "beat": "apm-test",
+                "pipeline": "apm",
+                "type": "_doc",
+                "version": "8.0.0"
+            },
+            "@timestamp": "2017-05-30T18:53:42.281Z",
+            "agent": {
+                "name": "elastic-node",
+                "version": "3.14.0"
+            },
+            "container": {
+                "id": "container-id"
+            },
+            "ecs": {
+                "version": "1.5.0"
+            },
+            "host": {
+                "architecture": "x64",
+                "ip": "127.0.0.1",
+                "os": {
+                    "platform": "darwin"
+                }
+            },
+            "kubernetes": {
+                "namespace": "namespace1",
+                "pod": {
+                    "name": "pod-name",
+                    "uid": "pod-uid"
+                }
+            },
+            "observer": {
+                "ephemeral_id": "00000000-0000-0000-0000-000000000000",
+                "hostname": "",
+                "id": "fbba762a-14dd-412c-b7e9-b79f903eb492",
+                "type": "test-apm-server",
+                "version": "8.0.0",
+                "version_major": 8
+            },
+            "process": {
+                "args": [
+                    "node",
+                    "server.js"
+                ],
+                "pid": 1234,
+                "ppid": 6789,
+                "title": "node"
+            },
+            "processor": {
+                "event": "transaction",
+                "name": "transaction"
+            },
+            "service": {
+                "environment": "staging",
+                "framework": {
+                    "name": "Express",
+                    "version": "1.2.3"
+                },
+                "language": {
+                    "name": "ecmascript",
+                    "version": "8"
+                },
+                "name": "1234_service-12a3",
+                "node": {
+                    "name": "container-id"
+                },
+                "runtime": {
+                    "name": "node",
+                    "version": "8.0.0"
+                },
+                "version": "5.1.3"
+            },
+            "timestamp": {
+                "us": 1496170422281999
+            },
+            "trace": {
+                "id": "85925e55b43f4342aaaaaaaaaaaaaaaa"
+            },
+            "transaction": {
+                "duration": {
+                    "us": 13980
+                },
+                "id": "85925e55b43f4342",
+                "name": "GET /api/types",
+                "result": "200",
+                "sampled": true,
+                "span_count": {
+                    "dropped": 258,
+                    "started": 1
+                },
+                "type": "request"
+            },
+            "user": {
+                "email": "foo@bar.com",
+                "id": "123user",
+                "name": "foo"
+            }
+        },
+        {
+            "@metadata": {
+                "beat": "apm-test",
+                "pipeline": "apm",
+                "type": "_doc",
+                "version": "8.0.0"
+            },
+            "@timestamp": "2017-05-30T18:53:42.281Z",
+            "agent": {
+                "name": "js-base",
+                "version": "1.3"
+            },
+            "container": {
+                "id": "container-id"
+            },
+            "destination": {
+                "address": "0:0::0:1",
+                "ip": "0:0::0:1",
+                "port": 5432
+            },
+            "ecs": {
+                "version": "1.5.0"
+            },
+            "host": {
+                "architecture": "x64",
+                "ip": "127.0.0.1",
+                "os": {
+                    "platform": "darwin"
+                }
+            },
+            "kubernetes": {
+                "namespace": "namespace1",
+                "pod": {
+                    "name": "pod-name",
+                    "uid": "pod-uid"
+                }
+            },
+            "observer": {
+                "ephemeral_id": "00000000-0000-0000-0000-000000000000",
+                "hostname": "",
+                "id": "fbba762a-14dd-412c-b7e9-b79f903eb492",
+                "type": "test-apm-server",
+                "version": "8.0.0",
+                "version_major": 8
+            },
+            "parent": {
+                "id": "85925e55b43f4342"
+            },
+            "process": {
+                "args": [
+                    "node",
+                    "server.js"
+                ],
+                "pid": 1234,
+                "ppid": 6789,
+                "title": "node"
+            },
+            "processor": {
+                "event": "span",
+                "name": "transaction"
+            },
+            "service": {
+                "environment": "staging",
+                "framework": {
+                    "name": "Express",
+                    "version": "1.2.3"
+                },
+                "language": {
+                    "name": "ecmascript",
+                    "version": "8"
+                },
+                "name": "serviceabc",
+                "node": {
+                    "name": "container-id"
+                },
+                "runtime": {
+                    "name": "javascript",
+                    "version": "8.0.0"
+                },
+                "version": "5.1.3"
+            },
+            "span": {
+                "action": "query.custom",
+                "db": {
+                    "instance": "customers",
+                    "statement": "SELECT * FROM product_types WHERE user_id=?",
+                    "type": "sql",
+                    "user": {
+                        "name": "readonly_user"
+                    }
+                },
+                "destination": {
+                    "service": {
+                        "name": "postgresql",
+                        "resource": "postgresql",
+                        "type": "db"
+                    }
+                },
+                "duration": {
+                    "us": 3781
+                },
+                "id": "15aaaaaaaaaaaaaa",
+                "name": "SELECT FROM product_types",
+                "start": {
+                    "us": 2830
+                },
+                "subtype": "postgresql",
+                "type": "db.postgresql.query"
+            },
+            "timestamp": {
+                "us": 1496170422281000
+            },
+            "trace": {
+                "id": "85925e55b43f4342aaaaaaaaaaaaaaaa"
+            },
+            "transaction": {
+                "id": "85925e55b43f4342"
+            },
+            "user": {
+                "email": "foo@bar.com",
+                "id": "123user",
+                "name": "foo"
+            }
+        }
+    ]
+}
diff --git a/changelogs/head.asciidoc b/changelogs/head.asciidoc
index 691e45575c8..60b24d7f8aa 100644
--- a/changelogs/head.asciidoc
+++ b/changelogs/head.asciidoc
@@ -19,3 +19,4 @@ https://github.com/elastic/apm-server/compare/7.7\...master[View commits]
 * RUM V3 endpoint {pull}3328[3328], {pull}3414[3414], {pull}3512[3512], {pull}3526[3526], {pull}3616[3616], {pull}3648[3648], {pull}3659[3659]
 * We now publish libbeat metrics through the /debug/vars endpoint {pull}3550[3550]
 * Introduce transaction.duration.histogram aggregation {pull}3651[3651]
+* Introduce config to drop unsampled transactions {pull}3702[3702]
diff --git a/publish/pub.go b/publish/pub.go
index 521586f6948..f2afb75b30c 100644
--- a/publish/pub.go
+++ b/publish/pub.go
@@ -132,6 +132,10 @@ func (p *Publisher) Stop() {
 // an error is returned.
 // Calling send after Stop will return an error.
 func (p *Publisher) Send(ctx context.Context, req PendingReq) error {
+	if len(req.Transformables) == 0 {
+		return nil
+	}
+
 	p.m.RLock()
 	defer p.m.RUnlock()
 	if p.stopped {
diff --git a/sampling/sampling.go b/sampling/sampling.go
new file mode 100644
index 00000000000..2504b750974
--- /dev/null
+++ b/sampling/sampling.go
@@ -0,0 +1,59 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package sampling
+
+import (
+	"context"
+
+	"github.com/elastic/apm-server/model"
+	"github.com/elastic/apm-server/publish"
+	"github.com/elastic/beats/v7/libbeat/monitoring"
+)
+
+var (
+	monitoringRegistry         = monitoring.Default.NewRegistry("apm-server.sampling")
+	transactionsDroppedCounter = monitoring.NewInt(monitoringRegistry, "transactions_dropped")
+)
+
+// NewDiscardUnsampledReporter returns a publish.Reporter which discards
+// unsampled transactions before deferring to reporter.
+//
+// The returned publish.Reporter does not guarantee order preservation of
+// reported events.
+func NewDiscardUnsampledReporter(reporter publish.Reporter) publish.Reporter {
+	return func(ctx context.Context, req publish.PendingReq) error {
+		var dropped int64
+		events := req.Transformables
+		for i := 0; i < len(events); {
+			tx, ok := events[i].(*model.Transaction)
+			if !ok || tx.Sampled == nil || *tx.Sampled {
+				i++
+				continue
+			}
+			n := len(req.Transformables)
+			events[i], events[n-1] = events[n-1], events[i]
+			events = events[:n-1]
+			dropped++
+		}
+		if dropped > 0 {
+			transactionsDroppedCounter.Add(dropped)
+		}
+		req.Transformables = events
+		return reporter(ctx, req)
+	}
+}
diff --git a/sampling/sampling_test.go b/sampling/sampling_test.go
new file mode 100644
index 00000000000..16452b3296a
--- /dev/null
+++ b/sampling/sampling_test.go
@@ -0,0 +1,72 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package sampling_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/elastic/apm-server/model"
+	"github.com/elastic/apm-server/publish"
+	"github.com/elastic/apm-server/sampling"
+	"github.com/elastic/apm-server/transform"
+	"github.com/elastic/beats/v7/libbeat/monitoring"
+)
+
+func TestNewDiscardUnsampledReporter(t *testing.T) {
+	var reported []transform.Transformable
+	reporter := sampling.NewDiscardUnsampledReporter(
+		func(ctx context.Context, req publish.PendingReq) error {
+			reported = req.Transformables
+			return nil
+		},
+	)
+
+	t1 := &model.Transaction{}
+	t2 := &model.Transaction{Sampled: newBool(false)}
+	t3 := &model.Transaction{Sampled: newBool(true)}
+	span := &model.Span{}
+
+	reporter(context.Background(), publish.PendingReq{
+		Transformables: []transform.Transformable{t1, t2, t3, span},
+	})
+
+	// Note that t3 gets sent to the back of the slice;
+	// this reporter is not order-preserving.
+	require.Len(t, reported, 3)
+	assert.Equal(t, t1, reported[0])
+	assert.Equal(t, span, reported[1])
+	assert.Equal(t, t3, reported[2])
+
+	expectedMonitoring := monitoring.MakeFlatSnapshot()
+	expectedMonitoring.Ints["transactions_dropped"] = 1
+
+	snapshot := monitoring.CollectFlatSnapshot(
+		monitoring.GetRegistry("apm-server.sampling"),
+		monitoring.Full,
+		false, // expvar
+	)
+	assert.Equal(t, expectedMonitoring, snapshot)
+}
+
+func newBool(v bool) *bool {
+	return &v
+}
diff --git a/tests/system/config/apm-server.yml.j2 b/tests/system/config/apm-server.yml.j2
index da96438157f..848cb6739d5 100644
--- a/tests/system/config/apm-server.yml.j2
+++ b/tests/system/config/apm-server.yml.j2
@@ -144,6 +144,9 @@ apm-server:
   aggregation.interval: {{ aggregation_interval }}
   {% endif %}
 
+  sampling:
+    keep_unsampled: {{ sampling_keep_unsampled }}
+
   {% if mode %}
   mode: {{ mode }}
   {% endif %}
diff --git a/tests/system/drop_unsampled_transactions.approved.json b/tests/system/drop_unsampled_transactions.approved.json
new file mode 100644
index 00000000000..0ce7272ca58
--- /dev/null
+++ b/tests/system/drop_unsampled_transactions.approved.json
@@ -0,0 +1,405 @@
+[
+    {
+        "@timestamp": "2017-05-30T18:53:42.281Z",
+        "agent": {
+            "name": "elastic-node",
+            "version": "3.14.0"
+        },
+        "container": {
+            "id": "container-id"
+        },
+        "ecs": {
+            "version": "1.5.0"
+        },
+        "event": {
+            "ingested": "2020-04-29T02:24:19.182874Z"
+        },
+        "host": {
+            "architecture": "x64",
+            "ip": "127.0.0.1",
+            "os": {
+                "platform": "darwin"
+            }
+        },
+        "kubernetes": {
+            "namespace": "namespace1",
+            "pod": {
+                "name": "pod-name",
+                "uid": "pod-uid"
+            }
+        },
+        "observer": {
+            "ephemeral_id": "ebd89158-9f85-469e-9bc0-9e19b174a1ba",
+            "hostname": "goat",
+            "id": "01019c57-ff25-4ddf-b9e9-2f421577a9a2",
+            "type": "apm-server",
+            "version": "8.0.0",
+            "version_major": 8
+        },
+        "process": {
+            "args": [
+                "node",
+                "server.js"
+            ],
+            "pid": 1234,
+            "ppid": 6789,
+            "title": "node"
+        },
+        "processor": {
+            "event": "transaction",
+            "name": "transaction"
+        },
+        "service": {
+            "environment": "staging",
+            "framework": {
+                "name": "Express",
+                "version": "1.2.3"
+            },
+            "language": {
+                "name": "ecmascript",
+                "version": "8"
+            },
+            "name": "1234_service-12a3",
+            "node": {
+                "name": "container-id"
+            },
+            "runtime": {
+                "name": "node",
+                "version": "8.0.0"
+            },
+            "version": "5.1.3"
+        },
+        "timestamp": {
+            "us": 1496170422281000
+        },
+        "trace": {
+            "id": "85925e55b43f4340aaaaaaaaaaaaaaaa"
+        },
+        "transaction": {
+            "duration": {
+                "us": 13980
+            },
+            "id": "85925e55b43f4340",
+            "name": "GET /api/types",
+            "result": "failure",
+            "sampled": true,
+            "span_count": {
+                "started": 0
+            },
+            "type": "request"
+        },
+        "user": {
+            "email": "foo@bar.com",
+            "id": "123user",
+            "name": "foo"
+        }
+    },
+    {
+        "@timestamp": "2017-05-30T18:53:42.281Z",
+        "agent": {
+            "name": "elastic-node",
+            "version": "3.14.0"
+        },
+        "container": {
+            "id": "container-id"
+        },
+        "ecs": {
+            "version": "1.5.0"
+        },
+        "event": {
+            "ingested": "2020-04-29T02:24:19.184164Z"
+        },
+        "host": {
+            "architecture": "x64",
+            "ip": "127.0.0.1",
+            "os": {
+                "platform": "darwin"
+            }
+        },
+        "kubernetes": {
+            "namespace": "namespace1",
+            "pod": {
+                "name": "pod-name",
+                "uid": "pod-uid"
+            }
+        },
+        "observer": {
+            "ephemeral_id": "ebd89158-9f85-469e-9bc0-9e19b174a1ba",
+            "hostname": "goat",
+            "id": "01019c57-ff25-4ddf-b9e9-2f421577a9a2",
+            "type": "apm-server",
+            "version": "8.0.0",
+            "version_major": 8
+        },
+        "process": {
+            "args": [
+                "node",
+                "server.js"
+            ],
+            "pid": 1234,
+            "ppid": 6789,
+            "title": "node"
+        },
+        "processor": {
+            "event": "transaction",
+            "name": "transaction"
+        },
+        "service": {
+            "environment": "staging",
+            "framework": {
+                "name": "Express",
+                "version": "1.2.3"
+            },
+            "language": {
+                "name": "ecmascript",
+                "version": "8"
+            },
+            "name": "1234_service-12a3",
+            "node": {
+                "name": "container-id"
+            },
+            "runtime": {
+                "name": "node",
+                "version": "8.0.0"
+            },
+            "version": "5.1.3"
+        },
+        "timestamp": {
+            "us": 1496170422281999
+        },
+        "trace": {
+            "id": "85925e55b43f4342aaaaaaaaaaaaaaaa"
+        },
+        "transaction": {
+            "duration": {
+                "us": 13980
+            },
+            "id": "85925e55b43f4342",
+            "name": "GET /api/types",
+            "result": "200",
+            "sampled": true,
+            "span_count": {
+                "dropped": 258,
+                "started": 1
+            },
+            "type": "request"
+        },
+        "user": {
+            "email": "foo@bar.com",
+            "id": "123user",
+            "name": "foo"
+        }
+    },
+    {
+        "@timestamp": "2017-05-30T18:53:27.154Z",
+        "agent": {
+            "name": "js-base",
+            "version": "1.3"
+        },
+        "client": {
+            "geo": {
+                "continent_name": "North America",
+                "country_iso_code": "US",
+                "location": {
+                    "lat": 37.751,
+                    "lon": -97.822
+                }
+            },
+            "ip": "8.8.8.8"
+        },
+        "container": {
+            "id": "container-id"
+        },
+        "ecs": {
+            "version": "1.5.0"
+        },
+        "event": {
+            "ingested": "2020-04-29T02:24:19.099344Z"
+        },
+        "host": {
+            "architecture": "x64",
+            "ip": "127.0.0.1",
+            "os": {
+                "platform": "darwin"
+            }
+        },
+        "http": {
+            "request": {
+                "body": {
+                    "original": {
+                        "additional": {
+                            "bar": 123,
+                            "req": "additional information"
+                        },
+                        "str": "hello world"
+                    }
+                },
+                "cookies": {
+                    "c1": "v1",
+                    "c2": "v2"
+                },
+                "env": {
+                    "GATEWAY_INTERFACE": "CGI/1.1",
+                    "SERVER_SOFTWARE": "nginx"
+                },
+                "headers": {
+                    "Array": [
+                        "foo",
+                        "bar",
+                        "baz"
+                    ],
+                    "Content-Type": [
+                        "text/html"
+                    ],
+                    "Cookie": [
+                        "c1=v1,c2=v2"
+                    ],
+                    "Some-Other-Header": [
+                        "foo"
+                    ],
+                    "User-Agent": [
+                        "Mozilla Chrome Edge"
+                    ]
+                },
+                "method": "post",
+                "socket": {
+                    "encrypted": true,
+                    "remote_address": "8.8.8.8"
+                }
+            },
+            "response": {
+                "finished": true,
+                "headers": {
+                    "Content-Type": [
+                        "application/json"
+                    ]
+                },
+                "headers_sent": true,
+                "status_code": 200
+            },
+            "version": "1.1"
+        },
+        "kubernetes": {
+            "namespace": "namespace1",
+            "pod": {
+                "name": "pod-name",
+                "uid": "pod-uid"
+            }
+        },
+        "labels": {
+            "bool_error": false,
+            "number_code": 2,
+            "organization_uuid": "9f0e9d64-c185-4d21-a6f4-4673ed561ec8"
+        },
+        "observer": {
+            "ephemeral_id": "ebd89158-9f85-469e-9bc0-9e19b174a1ba",
+            "hostname": "goat",
+            "id": "01019c57-ff25-4ddf-b9e9-2f421577a9a2",
+            "type": "apm-server",
+            "version": "8.0.0",
+            "version_major": 8
+        },
+        "process": {
+            "args": [
+                "node",
+                "server.js"
+            ],
+            "pid": 1234,
+            "ppid": 6789,
+            "title": "node"
+        },
+        "processor": {
+            "event": "transaction",
+            "name": "transaction"
+        },
+        "service": {
+            "environment": "staging",
+            "framework": {
+                "name": "Express",
+                "version": "1.2.3"
+            },
+            "language": {
+                "name": "ecmascript",
+                "version": "8"
+            },
+            "name": "serviceabc",
+            "node": {
+                "name": "special-name"
+            },
+            "runtime": {
+                "name": "javascript",
+                "version": "8.0.0"
+            },
+            "version": "5.1.3"
+        },
+        "source": {
+            "ip": "8.8.8.8"
+        },
+        "timestamp": {
+            "us": 1496170407154000
+        },
+        "trace": {
+            "id": "945254c567a5417eaaaaaaaaaaaaaaaa"
+        },
+        "transaction": {
+            "custom": {
+                "(": "not a valid regex and that is fine",
+                "and_objects": {
+                    "foo": [
+                        "bar",
+                        "baz"
+                    ]
+                },
+                "my_key": 1,
+                "some_other_value": "foo bar"
+            },
+            "duration": {
+                "us": 32592
+            },
+            "id": "945254c567a5417e",
+            "marks": {
+                "another_mark": {
+                    "some_float": 10,
+                    "some_long": 10
+                },
+                "navigationTiming": {
+                    "appBeforeBootstrap": 608.9300000000001,
+                    "navigationStart": -21
+                }
+            },
+            "name": "GET /api/types",
+            "page": {
+                "referer": "http://localhost:8000/test/e2e/",
+                "url": "http://localhost:8000/test/e2e/general-usecase/"
+            },
+            "result": "success",
+            "sampled": true,
+            "span_count": {
+                "dropped": 2,
+                "started": 4
+            },
+            "type": "request"
+        },
+        "url": {
+            "domain": "www.example.com",
+            "fragment": "#hash",
+            "full": "https://www.example.com/p/a/t/h?query=string#hash",
+            "original": "/p/a/t/h?query=string#hash",
+            "path": "/p/a/t/h",
+            "port": 8080,
+            "query": "?query=string",
+            "scheme": "https"
+        },
+        "user": {
+            "email": "foo@example.com",
+            "id": "99"
+        },
+        "user_agent": {
+            "device": {
+                "name": "Other"
+            },
+            "name": "Other",
+            "original": "Mozilla Chrome Edge"
+        }
+    }
+]
\ No newline at end of file
diff --git a/tests/system/keep_unsampled_transactions.approved.json b/tests/system/keep_unsampled_transactions.approved.json
new file mode 100644
index 00000000000..3997e639dc4
--- /dev/null
+++ b/tests/system/keep_unsampled_transactions.approved.json
@@ -0,0 +1,500 @@
+[
+    {
+        "@timestamp": "2017-05-30T18:53:42.281Z",
+        "agent": {
+            "name": "elastic-node",
+            "version": "3.14.0"
+        },
+        "container": {
+            "id": "container-id"
+        },
+        "ecs": {
+            "version": "1.5.0"
+        },
+        "event": {
+            "ingested": "2020-04-29T02:16:27.090771Z"
+        },
+        "host": {
+            "architecture": "x64",
+            "ip": "127.0.0.1",
+            "os": {
+                "platform": "darwin"
+            }
+        },
+        "kubernetes": {
+            "namespace": "namespace1",
+            "pod": {
+                "name": "pod-name",
+                "uid": "pod-uid"
+            }
+        },
+        "observer": {
+            "ephemeral_id": "3f31e73c-2fdf-4f39-8c81-57b25d00fc16",
+            "hostname": "goat",
+            "id": "0f00bacd-a23e-41c5-a2fb-4d90b2776018",
+            "type": "apm-server",
+            "version": "8.0.0",
+            "version_major": 8
+        },
+        "process": {
+            "args": [
+                "node",
+                "server.js"
+            ],
+            "pid": 1234,
+            "ppid": 6789,
+            "title": "node"
+        },
+        "processor": {
+            "event": "transaction",
+            "name": "transaction"
+        },
+        "service": {
+            "environment": "staging",
+            "framework": {
+                "name": "Express",
+                "version": "1.2.3"
+            },
+            "language": {
+                "name": "ecmascript",
+                "version": "8"
+            },
+            "name": "1234_service-12a3",
+            "node": {
+                "name": "container-id"
+            },
+            "runtime": {
+                "name": "node",
+                "version": "8.0.0"
+            },
+            "version": "5.1.3"
+        },
+        "timestamp": {
+            "us": 1496170422281000
+        },
+        "trace": {
+            "id": "85925e55b43f4340aaaaaaaaaaaaaaaa"
+        },
+        "transaction": {
+            "duration": {
+                "us": 13980
+            },
+            "id": "85925e55b43f4340",
+            "name": "GET /api/types",
+            "result": "failure",
+            "sampled": true,
+            "span_count": {
+                "started": 0
+            },
+            "type": "request"
+        },
+        "user": {
+            "email": "foo@bar.com",
+            "id": "123user",
+            "name": "foo"
+        }
+    },
+    {
+        "@timestamp": "2017-05-30T18:53:42.000Z",
+        "agent": {
+            "name": "elastic-node",
+            "version": "3.14.0"
+        },
+        "container": {
+            "id": "container-id"
+        },
+        "ecs": {
+            "version": "1.5.0"
+        },
+        "event": {
+            "ingested": "2020-04-29T02:16:27.091518Z"
+        },
+        "host": {
+            "architecture": "x64",
+            "ip": "127.0.0.1",
+            "os": {
+                "platform": "darwin"
+            }
+        },
+        "kubernetes": {
+            "namespace": "namespace1",
+            "pod": {
+                "name": "pod-name",
+                "uid": "pod-uid"
+            }
+        },
+        "observer": {
+            "ephemeral_id": "3f31e73c-2fdf-4f39-8c81-57b25d00fc16",
+            "hostname": "goat",
+            "id": "0f00bacd-a23e-41c5-a2fb-4d90b2776018",
+            "type": "apm-server",
+            "version": "8.0.0",
+            "version_major": 8
+        },
+        "process": {
+            "args": [
+                "node",
+                "server.js"
+            ],
+            "pid": 1234,
+            "ppid": 6789,
+            "title": "node"
+        },
+        "processor": {
+            "event": "transaction",
+            "name": "transaction"
+        },
+        "service": {
+            "environment": "staging",
+            "framework": {
+                "name": "Express",
+                "version": "1.2.3"
+            },
+            "language": {
+                "name": "ecmascript",
+                "version": "8"
+            },
+            "name": "1234_service-12a3",
+            "node": {
+                "name": "container-id"
+            },
+            "runtime": {
+                "name": "node",
+                "version": "8.0.0"
+            },
+            "version": "5.1.3"
+        },
+        "timestamp": {
+            "us": 1496170422000000
+        },
+        "trace": {
+            "id": "85925e55b43f4341aaaaaaaaaaaaaaaa"
+        },
+        "transaction": {
+            "duration": {
+                "us": 13980
+            },
+            "id": "85925e55b43f4341",
+            "name": "GET /api/types",
+            "result": "200",
+            "sampled": false,
+            "span_count": {
+                "started": 0
+            },
+            "type": "request"
+        },
+        "user": {
+            "email": "foo@bar.com",
+            "id": "123user",
+            "name": "foo"
+        }
+    },
+    {
+        "@timestamp": "2017-05-30T18:53:42.281Z",
+        "agent": {
+            "name": "elastic-node",
+            "version": "3.14.0"
+        },
+        "container": {
+            "id": "container-id"
+        },
+        "ecs": {
+            "version": "1.5.0"
+        },
+        "event": {
+            "ingested": "2020-04-29T02:16:27.092239Z"
+        },
+        "host": {
+            "architecture": "x64",
+            "ip": "127.0.0.1",
+            "os": {
+                "platform": "darwin"
+            }
+        },
+        "kubernetes": {
+            "namespace": "namespace1",
+            "pod": {
+                "name": "pod-name",
+                "uid": "pod-uid"
+            }
+        },
+        "observer": {
+            "ephemeral_id": "3f31e73c-2fdf-4f39-8c81-57b25d00fc16",
+            "hostname": "goat",
+            "id": "0f00bacd-a23e-41c5-a2fb-4d90b2776018",
+            "type": "apm-server",
+            "version": "8.0.0",
+            "version_major": 8
+        },
+        "process": {
+            "args": [
+                "node",
+                "server.js"
+            ],
+            "pid": 1234,
+            "ppid": 6789,
+            "title": "node"
+        },
+        "processor": {
+            "event": "transaction",
+            "name": "transaction"
+        },
+        "service": {
+            "environment": "staging",
+            "framework": {
+                "name": "Express",
+                "version": "1.2.3"
+            },
+            "language": {
+                "name": "ecmascript",
+                "version": "8"
+            },
+            "name": "1234_service-12a3",
+            "node": {
+                "name": "container-id"
+            },
+            "runtime": {
+                "name": "node",
+                "version": "8.0.0"
+            },
+            "version": "5.1.3"
+        },
+        "timestamp": {
+            "us": 1496170422281999
+        },
+        "trace": {
+            "id": "85925e55b43f4342aaaaaaaaaaaaaaaa"
+        },
+        "transaction": {
+            "duration": {
+                "us": 13980
+            },
+            "id": "85925e55b43f4342",
+            "name": "GET /api/types",
+            "result": "200",
+            "sampled": true,
+            "span_count": {
+                "dropped": 258,
+                "started": 1
+            },
+            "type": "request"
+        },
+        "user": {
+            "email": "foo@bar.com",
+            "id": "123user",
+            "name": "foo"
+        }
+    },
+    {
+        "@timestamp": "2017-05-30T18:53:27.154Z",
+        "agent": {
+            "name": "js-base",
+            "version": "1.3"
+        },
+        "client": {
+            "geo": {
+                "continent_name": "North America",
+                "country_iso_code": "US",
+                "location": {
+                    "lat": 37.751,
+                    "lon": -97.822
+                }
+            },
+            "ip": "8.8.8.8"
+        },
+        "container": {
+            "id": "container-id"
+        },
+        "ecs": {
+            "version": "1.5.0"
+        },
+        "event": {
+            "ingested": "2020-04-29T02:16:26.984994Z"
+        },
+        "host": {
+            "architecture": "x64",
+            "ip": "127.0.0.1",
+            "os": {
+                "platform": "darwin"
+            }
+        },
+        "http": {
+            "request": {
+                "body": {
+                    "original": {
+                        "additional": {
+                            "bar": 123,
+                            "req": "additional information"
+                        },
+                        "str": "hello world"
+                    }
+                },
+                "cookies": {
+                    "c1": "v1",
+                    "c2": "v2"
+                },
+                "env": {
+                    "GATEWAY_INTERFACE": "CGI/1.1",
+                    "SERVER_SOFTWARE": "nginx"
+                },
+                "headers": {
+                    "Array": [
+                        "foo",
+                        "bar",
+                        "baz"
+                    ],
+                    "Content-Type": [
+                        "text/html"
+                    ],
+                    "Cookie": [
+                        "c1=v1,c2=v2"
+                    ],
+                    "Some-Other-Header": [
+                        "foo"
+                    ],
+                    "User-Agent": [
+                        "Mozilla Chrome Edge"
+                    ]
+                },
+                "method": "post",
+                "socket": {
+                    "encrypted": true,
+                    "remote_address": "8.8.8.8"
+                }
+            },
+            "response": {
+                "finished": true,
+                "headers": {
+                    "Content-Type": [
+                        "application/json"
+                    ]
+                },
+                "headers_sent": true,
+                "status_code": 200
+            },
+            "version": "1.1"
+        },
+        "kubernetes": {
+            "namespace": "namespace1",
+            "pod": {
+                "name": "pod-name",
+                "uid": "pod-uid"
+            }
+        },
+        "labels": {
+            "bool_error": false,
+            "number_code": 2,
+            "organization_uuid": "9f0e9d64-c185-4d21-a6f4-4673ed561ec8"
+        },
+        "observer": {
+            "ephemeral_id": "3f31e73c-2fdf-4f39-8c81-57b25d00fc16",
+            "hostname": "goat",
+            "id": "0f00bacd-a23e-41c5-a2fb-4d90b2776018",
+            "type": "apm-server",
+            "version": "8.0.0",
+            "version_major": 8
+        },
+        "process": {
+            "args": [
+                "node",
+                "server.js"
+            ],
+            "pid": 1234,
+            "ppid": 6789,
+            "title": "node"
+        },
+        "processor": {
+            "event": "transaction",
+            "name": "transaction"
+        },
+        "service": {
+            "environment": "staging",
+            "framework": {
+                "name": "Express",
+                "version": "1.2.3"
+            },
+            "language": {
+                "name": "ecmascript",
+                "version": "8"
+            },
+            "name": "serviceabc",
+            "node": {
+                "name": "special-name"
+            },
+            "runtime": {
+                "name": "javascript",
+                "version": "8.0.0"
+            },
+            "version": "5.1.3"
+        },
+        "source": {
+            "ip": "8.8.8.8"
+        },
+        "timestamp": {
+            "us": 1496170407154000
+        },
+        "trace": {
+            "id": "945254c567a5417eaaaaaaaaaaaaaaaa"
+        },
+        "transaction": {
+            "custom": {
+                "(": "not a valid regex and that is fine",
+                "and_objects": {
+                    "foo": [
+                        "bar",
+                        "baz"
+                    ]
+                },
+                "my_key": 1,
+                "some_other_value": "foo bar"
+            },
+            "duration": {
+                "us": 32592
+            },
+            "id": "945254c567a5417e",
+            "marks": {
+                "another_mark": {
+                    "some_float": 10,
+                    "some_long": 10
+                },
+                "navigationTiming": {
+                    "appBeforeBootstrap": 608.9300000000001,
+                    "navigationStart": -21
+                }
+            },
+            "name": "GET /api/types",
+            "page": {
+                "referer": "http://localhost:8000/test/e2e/",
+                "url": "http://localhost:8000/test/e2e/general-usecase/"
+            },
+            "result": "success",
+            "sampled": true,
+            "span_count": {
+                "dropped": 2,
+                "started": 4
+            },
+            "type": "request"
+        },
+        "url": {
+            "domain": "www.example.com",
+            "fragment": "#hash",
+            "full": "https://www.example.com/p/a/t/h?query=string#hash",
+            "original": "/p/a/t/h?query=string#hash",
+            "path": "/p/a/t/h",
+            "port": 8080,
+            "query": "?query=string",
+            "scheme": "https"
+        },
+        "user": {
+            "email": "foo@example.com",
+            "id": "99"
+        },
+        "user_agent": {
+            "device": {
+                "name": "Other"
+            },
+            "name": "Other",
+            "original": "Mozilla Chrome Edge"
+        }
+    }
+]
\ No newline at end of file
diff --git a/tests/system/test_aggregation.py b/tests/system/test_aggregation.py
index 74bd23d32d2..4dc38325ceb 100644
--- a/tests/system/test_aggregation.py
+++ b/tests/system/test_aggregation.py
@@ -13,15 +13,19 @@ def config(self):
         cfg.update({
             "aggregation_enabled": True,
             "aggregation_interval": "1s",
+            # Drop unsampled transaction events,
+            # to show that we aggregate before they
+            # are dropped.
+            "sampling_keep_unsampled": False,
         })
         return cfg
 
     def test_transaction_metrics(self):
         self.load_docs_with_template(self.get_payload_path("transactions_spans.ndjson"),
-                                     self.intake_url, 'transaction', 9)
+                                     self.intake_url, 'transaction', 8)
         self.assert_no_logged_warnings()
 
-        self.wait_for_events('transaction', 4, index=index_transaction)
+        self.wait_for_events('transaction', 3, index=index_transaction)
 
         metric_docs = self.wait_for_events('metric', 3, index=index_metric)
         for doc in metric_docs:
diff --git a/tests/system/test_sampling.py b/tests/system/test_sampling.py
new file mode 100644
index 00000000000..410afa72812
--- /dev/null
+++ b/tests/system/test_sampling.py
@@ -0,0 +1,56 @@
+import time
+
+from apmserver import integration_test
+from apmserver import ClientSideElasticTest, ElasticTest, ExpvarBaseTest, ProcStartupFailureTest
+from helper import wait_until
+from es_helper import index_smap, index_metric, index_transaction
+
+
+@integration_test
+class TestKeepUnsampled(ElasticTest):
+    def config(self):
+        cfg = super(TestKeepUnsampled, self).config()
+        cfg.update({"sampling_keep_unsampled": True})
+        return cfg
+
+    def test(self):
+        self.load_docs_with_template(self.get_payload_path("transactions_spans.ndjson"),
+                                     self.intake_url, 'transaction', 9)
+        self.assert_no_logged_warnings()
+        docs = self.wait_for_events('transaction', 4, index=index_transaction)
+        self.approve_docs('keep_unsampled_transactions', docs)
+
+
+@integration_test
+class TestDropUnsampled(ElasticTest):
+    def config(self):
+        cfg = super(TestDropUnsampled, self).config()
+        cfg.update({
+            "sampling_keep_unsampled": False,
+            # Enable aggregation to avoid a warning.
+            "aggregation_enabled": True,
+        })
+        return cfg
+
+    def test(self):
+        self.load_docs_with_template(self.get_payload_path("transactions_spans.ndjson"),
+                                     self.intake_url, 'transaction', 8)
+        self.assert_no_logged_warnings()
+        docs = self.wait_for_events('transaction', 3, index=index_transaction)
+        self.approve_docs('drop_unsampled_transactions', docs)
+
+
+@integration_test
+class TestConfigWarning(ElasticTest):
+    def config(self):
+        cfg = super(TestConfigWarning, self).config()
+        cfg.update({
+            "sampling_keep_unsampled": False,
+            # Disable aggregation to force a warning.
+            "aggregation_enabled": False,
+        })
+        return cfg
+
+    def test(self):
+        expected = "apm-server.sampling.keep_unsampled and apm-server.aggregation.enabled are both false, which will lead to incorrect metrics being reported in the APM UI"
+        self.assertIn(expected, self.get_log())