diff --git a/README.md b/README.md
index c21b3df..8a5092a 100644
--- a/README.md
+++ b/README.md
@@ -53,7 +53,7 @@ with a dot, for backward-compatibility.
 
 ##### etag
 
-Enable or disable etag generation, defaults to true.
+Enable or disable etag generation, defaults to `true` unless the transform options is set.
 
 ##### extensions
 
@@ -70,9 +70,11 @@ in preferred order.
 
 ##### lastModified
 
-Enable or disable `Last-Modified` header, defaults to true. Uses the file
+Enable or disable `Last-Modified` header, defaults to `true`. Uses the file
 system's last modified value.
 
+If the `transform` option is set then the default is `false`.
+
 ##### maxAge
 
 Provide a max-age in milliseconds for http caching, defaults to 0.
@@ -83,6 +85,26 @@ This can also be a string accepted by the
 
 Serve files relative to `path`.
 
+##### Transform
+
+A function that consumes the file stream and produces a new (transformed) stream:
+```javascript
+function(stream) {return stream.pipe(replaceStream('tobi', 'peter'))}
+```
+ 
+Multiple transformations are possible: 
+```javascript
+function(stream) {
+  return stream
+  .pipe(replaceStream('tobi', 'peter'))
+  .pipe(replaceStream('peter', 'hans'))
+  .pipe(...)
+}
+```
+
+With transform the last-modified and etag defaults to `false` but can be overridden when
+a transform on the file's stream is expected to always generate the same result. 
+
 ### Events
 
 The `SendStream` is an event emitter and will emit the following events:
diff --git a/index.js b/index.js
index f63081d..c5cb732 100644
--- a/index.js
+++ b/index.js
@@ -81,9 +81,13 @@ function SendStream(req, path, options) {
   this.path = path;
   this.options = options;
 
+  this._transform = typeof options.transform === 'function'
+      ? options.transform
+      : undefined
+
   this._etag = options.etag !== undefined
     ? Boolean(options.etag)
-    : true
+    : (this._transform !== undefined ? false : true)
 
   this._dotfiles = options.dotfiles !== undefined
     ? options.dotfiles
@@ -114,7 +118,7 @@ function SendStream(req, path, options) {
 
   this._lastModified = options.lastModified !== undefined
     ? Boolean(options.lastModified)
-    : true
+    : (this._transform !== undefined ? false : true)
 
   this._maxage = options.maxAge || options.maxage
   this._maxage = typeof this._maxage === 'string'
@@ -553,7 +557,12 @@ SendStream.prototype.send = function(path, stat){
   }
 
   // content-length
-  res.setHeader('Content-Length', len);
+  if(this._transform === undefined){
+	res.setHeader('Content-Length', len);
+  }else{
+    //we don't know the content-length of the transformed data beforehand
+    res.setHeader('Transfer-Encoding', 'chunked');
+  }
 
   // HEAD support
   if ('HEAD' == req.method) return res.end();
@@ -651,9 +660,15 @@ SendStream.prototype.stream = function(path, options){
 
   // pipe
   var stream = fs.createReadStream(path, options);
+  
   this.emit('stream', stream);
+  
+  if(this._transform !== undefined){
+    stream = this._transform(stream);
+  }
+  
   stream.pipe(res);
-
+  
   // response finished, done with the fd
   onFinished(res, function onfinished(){
     finished = true;
diff --git a/package.json b/package.json
index e863a55..efda1e4 100644
--- a/package.json
+++ b/package.json
@@ -29,7 +29,8 @@
     "after": "0.8.1",
     "istanbul": "0.3.5",
     "mocha": "~2.1.0",
-    "supertest": "~0.15.0"
+    "supertest": "~0.15.0",
+    "replacestream": "~1.0.2"
   },
   "files": [
     "HISTORY.md",
diff --git a/test/send.js b/test/send.js
index 0ed4682..119192f 100644
--- a/test/send.js
+++ b/test/send.js
@@ -8,6 +8,7 @@ var http = require('http');
 var path = require('path');
 var request = require('supertest');
 var send = require('..')
+var replaceStream = require('replacestream')
 
 // test server
 
@@ -1103,6 +1104,50 @@ describe('send(file, options)', function(){
     })
   })
 
+  describe('transform', function(){
+    it('should transform the file contents', function(done){
+      var app = http.createServer(function(req, res){
+        send(req, 'test/fixtures/name.txt', {transform: function(stream) {return stream.pipe(replaceStream('tobi', 'peter'))}})
+        .pipe(res)
+      });
+
+      request(app)
+      .get('/name.txt')
+      .expect(shouldNotHaveHeader('Last-Modified'))
+      .expect(shouldNotHaveHeader('ETag'))
+      .expect(200, "peter", done)
+    })
+
+    it('should be possible to do mulitple transformations', function(done){
+      var transformFunc = function(stream) {
+        return stream
+        .pipe(replaceStream('tobi', 'peter'))
+        .pipe(replaceStream('peter', 'hans'))
+      }
+	  
+      var app = http.createServer(function(req, res){
+        send(req, 'test/fixtures/name.txt', {transform: transformFunc})
+        .pipe(res)
+      });
+	  
+      request(app)
+      .get('/name.txt')
+      .expect(200, "hans", done)
+    })
+
+    it('should be able to override last modified', function(done){
+      var app = http.createServer(function(req, res){
+        send(req, 'test/fixtures/name.txt', {lastModified: true, transform: function(stream) {return stream.pipe(replaceStream('tobi', 'peter'))}})
+        .pipe(res)
+      });
+
+      request(app)
+      .get('/name.txt')
+      .expect('last-modified', dateRegExp)
+      .expect(200, "peter", done)
+    })
+  })
+
   describe('root', function(){
     describe('when given', function(){
       it('should join root', function(done){