diff --git a/docs/api.md b/docs/api.md
index 7fd47a5..0a89223 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -192,9 +192,9 @@ app.context({
   if you have a typo an error will be thrown, displaying this list
   so you can make a correction.
 
-### ctx.hasContent
+### ctx.length=
 
-  When the response status is __204__ or __304__ this returns __false__.
+  Set response Content-Length to the given value.
 
 ### ctx.length
 
@@ -219,12 +219,27 @@ app.context({
   - `Buffer` written
   - `Stream` piped
   - `Object` json-stringified
+  - `null` no content response
 
-  When a Koa application is created it injects
-  a middleware named `respond`, which handles
-  each of these `ctx.body` values. The `Content-Length`
-  header field is set when possible, and objects are 
-  passed through `JSON.stringify()`.
+#### String
+
+  The Content-Type is defaulted to text/html or text/plain, both with
+  a default charset of utf-8. The Content-Length field is also set.
+
+#### Buffer
+
+  The Content-Type is defaulted to application/octet-stream, and Content-Length
+  is also set.
+
+#### Stream
+
+  The Content-Type is defaulted to application/octet-stream.
+
+#### Object
+
+  The Content-Type is defaulted to application/json.
+
+#### Notes
 
   To alter the JSON response formatting use the `app.jsonSpaces`
   setting, for example to compress JSON responses set:
diff --git a/lib/application.js b/lib/application.js
index a232ec4..dcabf72 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -165,7 +165,7 @@ function respond(next){
     var res = this.res;
     var body = this.body;
     var head = 'HEAD' == this.method;
-    var ignore = 204 == this.status || 304 == this.status;
+    var noContent = 204 == this.status || 304 == this.status;
 
     // 404
     if (null == body && 200 == this.status) {
@@ -173,28 +173,22 @@ function respond(next){
     }
 
     // ignore body
-    if (ignore) return res.end();
+    if (noContent) return res.end();
 
     // status body
     if (null == body) {
-      this.set('Content-Type', 'text/plain');
+      this.type = 'text';
       body = http.STATUS_CODES[this.status];
     }
 
     // Buffer body
     if (Buffer.isBuffer(body)) {
-      var ct = this.responseHeader['content-type'];
-      if (!ct) this.set('Content-Type', 'application/octet-stream');
-      this.set('Content-Length', body.length);
       if (head) return res.end();
       return res.end(body);
     }
 
     // string body
     if ('string' == typeof body) {
-      var ct = this.responseHeader['content-type'];
-      if (!ct) this.set('Content-Type', 'text/plain; charset=utf-8');
-      this.set('Content-Length', Buffer.byteLength(body));
       if (head) return res.end();
       return res.end(body);
     }
@@ -208,8 +202,7 @@ function respond(next){
 
     // body: json
     body = JSON.stringify(body, null, this.app.jsonSpaces);
-    this.set('Content-Length', Buffer.byteLength(body));
-    this.set('Content-Type', 'application/json');
+    this.length = Buffer.byteLength(body);
     if (head) return res.end();
     res.end(body);
   }
diff --git a/lib/context.js b/lib/context.js
index fcf882a..592aadd 100644
--- a/lib/context.js
+++ b/lib/context.js
@@ -7,6 +7,7 @@ var debug = require('debug')('koa:context');
 var Negotiator = require('negotiator');
 var statuses = require('./status');
 var qs = require('querystring');
+var Stream = require('stream');
 var fresh = require('fresh');
 var http = require('http');
 var path = require('path');
@@ -46,53 +47,6 @@ module.exports = {
     return this.res._headers || {};
   },
 
-  /**
-   * Get response status code.
-   *
-   * @return {Number}
-   * @api public
-   */
-
-  get status() {
-    return this.res.statusCode;
-  },
-
-  /**
-   * Set response status code.
-   *
-   * @param {Number|String} val
-   * @api public
-   */
-
-  set status(val) {
-    if ('string' == typeof val) {
-      var n = statuses[val.toLowerCase()];
-      if (!n) throw new Error(statusError(val));
-      val = n;
-    }
-
-    this.res.statusCode = val;
-
-    if (!this.hasContent) {
-      this.res.removeHeader('Content-Type');
-      this.res.removeHeader('Content-Length');
-      this.res.removeHeader('Transfer-Encoding');
-    }
-  },
-
-  /**
-   * Check if the response has content,
-   * aka is not a 204 or 304 response.
-   *
-   * @return {Boolean}
-   * @api public
-   */
-
-  get hasContent() {
-    var s = this.status;
-    return 204 != s && 304 != s;
-  },
-
   /**
    * Return response status string.
    *
@@ -147,6 +101,94 @@ module.exports = {
     this.req.method = val;
   },
 
+  /**
+   * Get response status code.
+   *
+   * @return {Number}
+   * @api public
+   */
+
+  get status() {
+    return this.res.statusCode;
+  },
+
+  /**
+   * Set response status code.
+   *
+   * @param {Number|String} val
+   * @api public
+   */
+
+  set status(val) {
+    if ('string' == typeof val) {
+      var n = statuses[val.toLowerCase()];
+      if (!n) throw new Error(statusError(val));
+      val = n;
+    }
+
+    this.res.statusCode = val;
+
+    var noContent = 304 == this.status || 204 == this.status;
+    if (noContent && this.body) this.body = null;
+  },
+
+  /**
+   * Get response body.
+   *
+   * @return {Mixed}
+   * @api public
+   */
+
+  get body() {
+    return this._body;
+  },
+
+  /**
+   * Set response body.
+   *
+   * @param {String|Buffer|Object|Stream} val
+   * @api public
+   */
+
+  set body(val) {
+    this._body = val;
+
+    if (this.type) return;
+
+    // no content
+    if (null == val) {
+      var s = this.status;
+      this.status = 304 == s ? 304 : 204;
+      this.res.removeHeader('Content-Type');
+      this.res.removeHeader('Content-Length');
+      this.res.removeHeader('Transfer-Encoding');
+      return;
+    }
+
+    // string
+    if ('string' == typeof val) {
+      this.type = ~val.indexOf('<') ? 'html' : 'text';
+      this.length = Buffer.byteLength(val);
+      return;
+    }
+
+    // buffer
+    if (Buffer.isBuffer(val)) {
+      this.type = 'bin';
+      this.length = val.length;
+      return;
+    }
+
+    // stream
+    if (val instanceof Stream) {
+      this.type = 'bin';
+      return;
+    }
+
+    // json
+    this.type = 'json';
+  },
+
   /**
    * Get request pathname.
    *
@@ -314,6 +356,17 @@ module.exports = {
     return ~~len;
   },
 
+  /**
+   * Set Content-Length field to `n`.
+   *
+   * @param {Number} n
+   * @api public
+   */
+
+  set length(n) {
+    this.set('Content-Length', n);
+  },
+
   /**
    * Return parsed response Content-Length when present.
    *
diff --git a/test/application.js b/test/application.js
index 57ff6ca..e4ebbf9 100644
--- a/test/application.js
+++ b/test/application.js
@@ -90,7 +90,6 @@ describe('app.respond', function(){
       app.use(function(next){
         return function *(){
           this.status = 400;
-          this.body = null;
         }
       });
 
diff --git a/test/context.js b/test/context.js
index ea364c5..aff3021 100644
--- a/test/context.js
+++ b/test/context.js
@@ -21,6 +21,60 @@ function context(req, res) {
   return ctx;
 }
 
+describe('ctx.body=', function(){
+  describe('when a string is given', function(){
+    it('should default to text', function(){
+      var ctx = context();
+      ctx.body = 'Tobi';
+      assert('text/plain; charset=utf-8' == ctx.responseHeader['content-type']);
+    })
+
+    it('should set length', function(){
+      var ctx = context();
+      ctx.body = 'Tobi';
+      assert('4' == ctx.responseHeader['content-length']);
+    })
+  })
+
+  describe('when an html string is given', function(){
+    it('should default to html', function(){
+      var ctx = context();
+      ctx.body = '<h1>Tobi</h1>';
+      assert('text/html; charset=utf-8' == ctx.responseHeader['content-type']);
+    })
+  })
+
+  describe('when a stream is given', function(){
+    it('should default to an octet stream', function(){
+      var ctx = context();
+      ctx.body = fs.createReadStream('LICENSE');
+      assert('application/octet-stream' == ctx.responseHeader['content-type']);
+    })
+  })
+
+  describe('when a buffer is given', function(){
+    it('should default to an octet stream', function(){
+      var ctx = context();
+      ctx.body = new Buffer('hey');
+      assert('application/octet-stream' == ctx.responseHeader['content-type']);
+    })
+
+    it('should set length', function(){
+      var ctx = context();
+      ctx.body = new Buffer('Tobi');
+      assert('4' == ctx.responseHeader['content-length']);
+    })
+  })
+
+  describe('when an object is given', function(){
+    it('should default to json', function(){
+      var ctx = context();
+      ctx.body = { foo: 'bar' };
+      assert('application/json' == ctx.responseHeader['content-type']);
+    })
+  })
+})
+
 describe('ctx.error(msg)', function(){
   it('should set .status to 500', function(done){
     var ctx = context();
@@ -91,9 +145,6 @@ describe('ctx.responseLength', function(){
 
         ctx.body = new Buffer('foo');
         ctx.responseLength.should.equal(3);
-
-        ctx.body = {};
-        assert(null == ctx.responseLength);
       })
     })
 
@@ -227,6 +278,7 @@ describe('ctx.status=', function(){
 
       app.use(function(next){
         return function *(){
+          this.body = { foo: 'bar' };
           this.set('Content-Type', 'application/json');
           this.set('Content-Length', '15');
           this.set('Transfer-Encoding', 'chunked');