diff --git a/lib/buffer.js b/lib/buffer.js
deleted file mode 100644
index 6787881..0000000
--- a/lib/buffer.js
+++ /dev/null
@@ -1,32 +0,0 @@
-
-/*!
- * Canvas - Buffer
- * Copyright (c) 2010 LearnBoost <tj@learnboost.com>
- * MIT Licensed
- */
-
-/**
- * Concatenate `this` Buffer with `other`.
- *
- * @param {Buffer} other
- * @return {Buffer}
- * @api public
- */
-
-Buffer.prototype.concat = function(other) {
-  var len = this.length
-    , buf = new Buffer(len + other.length);
-  this.copy(buf, 0, 0);
-  other.copy(buf, len, 0);
-  return buf;
-};
-
-// patch if not v0.2 of node.js and Buffer.isBuffer fails for SlowBuffer
-if (process.version.indexOf("v0.2") == -1) {
-    var SlowBuffer = process.binding('buffer').SlowBuffer;
-    if (!Buffer.isBuffer(new SlowBuffer(10))) {
-        Buffer.isBuffer = function (b) {
-            return (b instanceof Buffer) || (b instanceof SlowBuffer);
-        };
-    }
-}
\ No newline at end of file
diff --git a/lib/canvas.js b/lib/canvas.js
index e363504..90c74e5 100644
--- a/lib/canvas.js
+++ b/lib/canvas.js
@@ -41,12 +41,6 @@ exports.cairoVersion = cairoVersion;
 exports.Context2d = Context2d;
 exports.PNGStream = PNGStream;
 
-/**
- * Buffer extensions.
- */
-
-require('./buffer');
-
 /**
  * Context2d implementation.
  */
@@ -104,37 +98,33 @@ Canvas.prototype.createSyncPNGStream = function(){
 };
 
 /**
- * Return a `Buffer` instance consisting of the PNG image data.
- *
- * @return {Buffer}
- * @api public
- */
-
-Canvas.prototype.toBuffer = function(){
-  var buf;
-  this.streamPNGSync(function(err, chunk, len){
-    if (err) throw err;
-    if (len) {
-      buf = buf
-        ? buf.concat(chunk)
-        : chunk;
-    }
-  });
-  return buf;
-};
-
-/**
- * Return a data url.
+ * Return a data url. Pass a function for async support.
  *
- * @param {String} type
+ * @param {String|Function} type
+ * @param {Function} fn
  * @return {String}
  * @api public
  */
 
-Canvas.prototype.toDataURL = function(type){
-  // TODO: jpeg / svg / pdf :)
+Canvas.prototype.toDataURL = function(type, fn){
+  // Default to png
   type = type || 'image/png';
+
+  // Allow callback as first arg
+  if ('function' == typeof type) fn = type, type = 'image/png';
+
+  // Throw on non-png
   if ('image/png' != type) throw new Error('currently only image/png is supported');
-  return 'data:' + type
-    + ';base64,' + this.toBuffer().toString('base64');
+
+  var prefix = 'data:' + type + ';base64,';
+
+  if (fn) {
+    this.toBuffer(function(err, buf){
+      if (err) return fn(err);
+      var str = 'data:' + type
+      fn(null, prefix + buf.toString('base64'));
+    });
+  } else {
+    return prefix + this.toBuffer().toString('base64');
+  }
 };
diff --git a/src/Canvas.cc b/src/Canvas.cc
index f0c2e21..6536db6 100644
--- a/src/Canvas.cc
+++ b/src/Canvas.cc
@@ -18,7 +18,12 @@ using namespace node;
  */
 
 typedef struct {
+  Persistent<Function> pfn;
   Handle<Function> fn;
+  unsigned len;
+  uint8_t *data;
+  Canvas *canvas;
+  cairo_status_t status;
 } closure_t;
 
 /*
@@ -33,6 +38,7 @@ Canvas::Initialize(Handle<Object> target) {
   t->SetClassName(String::NewSymbol("Canvas"));
 
   Local<ObjectTemplate> proto = t->PrototypeTemplate();
+  NODE_SET_PROTOTYPE_METHOD(t, "toBuffer", ToBuffer);
   NODE_SET_PROTOTYPE_METHOD(t, "streamPNGSync", StreamPNGSync);
   proto->SetAccessor(String::NewSymbol("width"), GetWidth, SetWidth);
   proto->SetAccessor(String::NewSymbol("height"), GetHeight, SetHeight);
@@ -102,12 +108,113 @@ Canvas::SetHeight(Local<String> prop, Local<Value> val, const AccessorInfo &info
   }
 }
 
+/*
+ * Canvas::ToBuffer callback.
+ */
+
+static cairo_status_t
+toBuffer(void *c, const uint8_t *data, unsigned len) {
+  closure_t *closure = (closure_t *) c;
+  // TODO: mem handling
+  if (closure->len) {
+    closure->data = (uint8_t *) realloc(closure->data, closure->len + len);
+    memcpy(closure->data + closure->len, data, len);
+    closure->len += len;
+  } else {
+    closure->data = (uint8_t *) malloc(len);
+    memcpy(closure->data, data, len);
+    closure->len += len;
+  }
+  return CAIRO_STATUS_SUCCESS;
+}
+
+/*
+ * EIO toBuffer callback.
+ */
+
+static int
+EIO_ToBuffer(eio_req *req) {
+  closure_t *closure = (closure_t *) req->data;
+
+  closure->status = cairo_surface_write_to_png_stream(
+      closure->canvas->getSurface()
+    , toBuffer
+    , closure);
+
+  return 0;
+}
+
+/*
+ * EIO after toBuffer callback.
+ */
+
+static int
+EIO_AfterToBuffer(eio_req *req) {
+  HandleScope scope;
+  closure_t *closure = (closure_t *) req->data;
+  ev_unref(EV_DEFAULT_UC);
+
+  if (closure->status) {
+    Handle<Value> argv[1] = { Canvas::Error(closure->status) };
+    closure->pfn->Call(Context::GetCurrent()->Global(), 1, argv);
+  } else {
+    Buffer *buf = Buffer::New(closure->len);
+    memcpy(buf->data(), closure->data, closure->len);
+    Handle<Value> argv[2] = { Null(), buf->handle_ };
+    closure->pfn->Call(Context::GetCurrent()->Global(), 2, argv);
+  }
+
+  closure->pfn.Dispose();
+  delete closure;
+  return 0;
+}
+
+/*
+ * Convert PNG data to a node::Buffer, async when a 
+ * callback function is passed.
+ */
+
+Handle<Value>
+Canvas::ToBuffer(const Arguments &args) {
+  HandleScope scope;
+  Canvas *canvas = ObjectWrap::Unwrap<Canvas>(args.This());
+
+  // Async
+  if (args[0]->IsFunction()) {
+    closure_t *closure = new closure_t;
+    closure->len = 0;
+    closure->canvas = canvas;
+    // TODO: only one callback fn in closure
+    canvas->Ref();
+    closure->pfn = Persistent<Function>::New(Handle<Function>::Cast(args[0]));
+    eio_custom(EIO_ToBuffer, EIO_PRI_DEFAULT, EIO_AfterToBuffer, closure);
+    ev_ref(EV_DEFAULT_UC);
+    return Undefined();
+  } else {
+    closure_t closure;
+    closure.len = 0;
+
+    TryCatch try_catch;
+    cairo_status_t status = cairo_surface_write_to_png_stream(canvas->getSurface(), toBuffer, &closure);
+
+    if (try_catch.HasCaught()) {
+      return try_catch.ReThrow();
+    } else if (status) {
+      return ThrowException(Canvas::Error(status));
+    } else {
+      Buffer *buf = Buffer::New(closure.len);
+      memcpy(buf->data(), closure.data, closure.len);
+      return buf->handle_;
+    }
+  }
+}
+
 /*
  * Canvas::StreamPNG callback.
  */
 
 static cairo_status_t
-writeToBuffer(void *c, const uint8_t *data, unsigned len) {
+streamPNG(void *c, const uint8_t *data, unsigned len) {
   closure_t *closure = (closure_t *) c;
   Buffer *buf = Buffer::New(len);
 #if NODE_VERSION_AT_LEAST(0,3,0)
@@ -136,7 +243,7 @@ Canvas::StreamPNGSync(const Arguments &args) {
   closure.fn = Handle<Function>::Cast(args[0]);
 
   TryCatch try_catch;
-  cairo_status_t status = cairo_surface_write_to_png_stream(canvas->getSurface(), writeToBuffer, &closure);
+  cairo_status_t status = cairo_surface_write_to_png_stream(canvas->getSurface(), streamPNG, &closure);
 
   if (try_catch.HasCaught()) {
     return try_catch.ReThrow();
diff --git a/src/Canvas.h b/src/Canvas.h
index 182a126..6902b26 100644
--- a/src/Canvas.h
+++ b/src/Canvas.h
@@ -52,6 +52,7 @@ class Canvas: public node::ObjectWrap {
     int height;
     static void Initialize(Handle<Object> target);
     static Handle<Value> New(const Arguments &args);
+    static Handle<Value> ToBuffer(const Arguments &args);
     static Handle<Value> GetWidth(Local<String> prop, const AccessorInfo &info);
     static Handle<Value> GetHeight(Local<String> prop, const AccessorInfo &info);
     static void SetWidth(Local<String> prop, Local<Value> val, const AccessorInfo &info);
diff --git a/test/canvas.test.js b/test/canvas.test.js
index bb0e766..44a8a43 100644
--- a/test/canvas.test.js
+++ b/test/canvas.test.js
@@ -237,7 +237,17 @@ module.exports = {
   },
   
   'test Canvas#toBuffer()': function(assert){
-    assert.ok(Buffer.isBuffer(new Canvas(200, 200).toBuffer()), 'Canvas#toBuffer() failed');
+    var buf = new Canvas(200,200).toBuffer();
+    assert.equal('PNG', buf.slice(1,4).toString());
+    assert.length(buf, 252);
+  },
+  
+  'test Canvas#toBuffer() async': function(assert){
+    new Canvas(200, 200).toBuffer(function(err, buf){
+      assert.ok(!err);
+      assert.equal('PNG', buf.slice(1,4).toString());
+      assert.length(buf, 252);
+    });
   },
   
   'test Canvas#toDataURL()': function(assert){
@@ -261,7 +271,7 @@ module.exports = {
     
     assert.equal(str, canvas.toDataURL(), 'Canvas#toDataURL() failed');
     assert.equal(str, canvas.toDataURL('image/png'), 'Canvas#toDataURL() failed');
-    
+
     var err;
     try {
       canvas.toDataURL('image/jpeg');
@@ -269,5 +279,19 @@ module.exports = {
       err = e;
     }
     assert.equal('currently only image/png is supported', err.message);
+  },
+  
+  'test Canvas#toDataURL() async': function(assert){
+    new Canvas(200,200).toDataURL(function(err, str){
+      assert.ok(!err);
+      assert.length(str, 358);
+    });
+  },
+  
+  'test Canvas#toDataURL() async with type': function(assert){
+    new Canvas(200,200).toDataURL('image/png', function(err, str){
+      assert.ok(!err);
+      assert.length(str, 358);
+    });
   }
 }
\ No newline at end of file