diff --git a/rclpy/services/minimal_client/client.py b/rclpy/services/minimal_client/client.py
index 17fbe330..7a25ccfa 100644
--- a/rclpy/services/minimal_client/client.py
+++ b/rclpy/services/minimal_client/client.py
@@ -28,16 +28,15 @@ def main(args=None):
     while not cli.wait_for_service(timeout_sec=1.0):
         node.get_logger().info('service not available, waiting again...')
 
-    cli.call(req)
-    # when calling wait for future
-    # spin should not be called in the main loop
-    cli.wait_for_future()
-    # TODO(mikaelarguedas) This is not the final API, and this does not scale
-    # for multiple pending requests. This will change once an executor model is implemented
-    # In the future the response will not be stored in cli.response
-    node.get_logger().info(
-        'Result of add_two_ints: for %d + %d = %d' %
-        (req.a, req.b, cli.response.sum))
+    future = cli.call_async(req)
+    rclpy.spin_until_future_complete(node, future)
+
+    if future.result() is not None:
+        node.get_logger().info(
+            'Result of add_two_ints: for %d + %d = %d' %
+            (req.a, req.b, future.result().sum))
+    else:
+        node.get_logger().info('Service call failed %r' % (future.exception(),))
 
     node.destroy_node()
     rclpy.shutdown()
diff --git a/rclpy/services/minimal_client/client_async.py b/rclpy/services/minimal_client/client_async.py
index f32b412e..ab3ae283 100644
--- a/rclpy/services/minimal_client/client_async.py
+++ b/rclpy/services/minimal_client/client_async.py
@@ -30,17 +30,17 @@ def main(args=None):
     while not cli.wait_for_service(timeout_sec=1.0):
         node.get_logger().info('service not available, waiting again...')
 
-    cli.call(req)
+    future = cli.call_async(req)
     while rclpy.ok():
-        # TODO(mikaelarguedas) This is not the final API, and this does not scale
-        # for multiple pending requests. This will change once an executor model is implemented
-        # In the future the response will not be stored in cli.response
-        if cli.response is not None:
-            node.get_logger().info(
-                'Result of add_two_ints: for %d + %d = %d' %
-                (req.a, req.b, cli.response.sum))
-            break
         rclpy.spin_once(node)
+        if future.done():
+            if future.result() is not None:
+                node.get_logger().info(
+                    'Result of add_two_ints: for %d + %d = %d' %
+                    (req.a, req.b, future.result().sum))
+            else:
+                node.get_logger().info('Service call failed %r' % (future.exception(),))
+            break
 
     node.destroy_node()
     rclpy.shutdown()
diff --git a/rclpy/services/minimal_client/client_async_callback.py b/rclpy/services/minimal_client/client_async_callback.py
new file mode 100644
index 00000000..bb0a90ee
--- /dev/null
+++ b/rclpy/services/minimal_client/client_async_callback.py
@@ -0,0 +1,70 @@
+# Copyright 2018 Open Source Robotics Foundation, Inc.
+#
+# Licensed 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.
+
+from example_interfaces.srv import AddTwoInts
+
+import rclpy
+from rclpy.callback_groups import ReentrantCallbackGroup
+
+
+def main(args=None):
+    rclpy.init(args=args)
+    node = rclpy.create_node('minimal_client')
+    # Node's default callback group is mutually exclusive. This would prevent the client response
+    # from being processed until the timer callback finished, but the timer callback in this
+    # example is waiting for the client response
+    cb_group = ReentrantCallbackGroup()
+    cli = node.create_client(AddTwoInts, 'add_two_ints', callback_group=cb_group)
+    did_run = False
+    did_get_result = False
+
+    async def call_service():
+        nonlocal cli, node, did_run, did_get_result
+        did_run = True
+        try:
+            req = AddTwoInts.Request()
+            req.a = 41
+            req.b = 1
+            future = cli.call_async(req)
+            result = await future
+            if result is not None:
+                node.get_logger().info(
+                    'Result of add_two_ints: for %d + %d = %d' %
+                    (req.a, req.b, result.sum))
+            else:
+                node.get_logger().info('Service call failed %r' % (future.exception(),))
+        finally:
+            did_get_result = True
+
+    while not cli.wait_for_service(timeout_sec=1.0):
+        node.get_logger().info('service not available, waiting again...')
+
+    timer = node.create_timer(0.5, call_service, callback_group=cb_group)
+
+    while rclpy.ok() and not did_run:
+        rclpy.spin_once(node)
+
+    if did_run:
+        # call timer callback only once
+        timer.cancel()
+
+    while rclpy.ok() and not did_get_result:
+        rclpy.spin_once(node)
+
+    node.destroy_node()
+    rclpy.shutdown()
+
+
+if __name__ == '__main__':
+    main()
diff --git a/rclpy/services/minimal_client/client_async_member_function.py b/rclpy/services/minimal_client/client_async_member_function.py
index 60b0a683..f320b15e 100644
--- a/rclpy/services/minimal_client/client_async_member_function.py
+++ b/rclpy/services/minimal_client/client_async_member_function.py
@@ -30,7 +30,7 @@ def __init__(self):
     def send_request(self):
         self.req.a = 41
         self.req.b = 1
-        self.cli.call(self.req)
+        self.future = self.cli.call_async(self.req)
 
 
 def main(args=None):
@@ -40,15 +40,17 @@ def main(args=None):
     minimal_client.send_request()
 
     while rclpy.ok():
-        # TODO(mikaelarguedas) This is not the final API, and this does not scale
-        # for multiple pending requests. This will change once an executor model is implemented
-        # In the future the response will not be stored in cli.response
-        if minimal_client.cli.response is not None:
-            minimal_client.get_logger().info(
-                'Result of add_two_ints: for %d + %d = %d' %
-                (minimal_client.req.a, minimal_client.req.b, minimal_client.cli.response.sum))
-            break
         rclpy.spin_once(minimal_client)
+        if minimal_client.future.done():
+            if minimal_client.future.result() is not None:
+                response = minimal_client.future.result()
+                minimal_client.get_logger().info(
+                    'Result of add_two_ints: for %d + %d = %d' %
+                    (minimal_client.req.a, minimal_client.req.b, response.sum))
+            else:
+                minimal_client.get_logger().info(
+                    'Service call failed %r' % (minimal_client.future.exception(),))
+            break
 
     minimal_client.destroy_node()
     rclpy.shutdown()
diff --git a/rclpy/services/minimal_client/setup.py b/rclpy/services/minimal_client/setup.py
index 28cf684a..8f8c0b20 100644
--- a/rclpy/services/minimal_client/setup.py
+++ b/rclpy/services/minimal_client/setup.py
@@ -9,7 +9,8 @@
     py_modules=[
         'client',
         'client_async',
-        'client_async_member_function'],
+        'client_async_member_function',
+        'client_async_callback'],
     data_files=[
         ('share/ament_index/resource_index/packages',
             ['resource/' + package_name]),
@@ -36,6 +37,7 @@
             'client_async = client_async:main',
             'client_async_member_function ='
             ' client_async_member_function:main',
+            'client_async_callback = client_async_callback:main',
         ],
     },
 )