diff --git a/benchmark/http/client-request-body.js b/benchmark/http/client-request-body.js
new file mode 100644
index 0000000000..7a3468a670
--- /dev/null
+++ b/benchmark/http/client-request-body.js
@@ -0,0 +1,69 @@
+// Measure the time it takes for the HTTP client to send a request body.
+
+var common = require('../common.js');
+var http = require('http');
+
+var bench = common.createBenchmark(main, {
+  dur: [5],
+  type: ['asc', 'utf', 'buf'],
+  bytes: [32, 256, 1024],
+  method: ['write', 'end  '] // two spaces added to line up each row
+});
+
+function main(conf) {
+  var dur = +conf.dur;
+  var len = +conf.bytes;
+
+  var encoding;
+  var chunk;
+  switch (conf.type) {
+    case 'buf':
+      chunk = new Buffer(len);
+      chunk.fill('x');
+      break;
+    case 'utf':
+      encoding = 'utf8';
+      chunk = new Array(len / 2 + 1).join('ü');
+      break;
+    case 'asc':
+      chunk = new Array(len + 1).join('a');
+      break;
+  }
+
+  var nreqs = 0;
+  var options = {
+    headers: { 'Connection': 'keep-alive', 'Transfer-Encoding': 'chunked' },
+    agent: new http.Agent({ maxSockets: 1 }),
+    host: '127.0.0.1',
+    port: common.PORT,
+    path: '/',
+    method: 'POST'
+  };
+
+  var server = http.createServer(function(req, res) {
+    res.end();
+  });
+  server.listen(options.port, options.host, function() {
+    setTimeout(done, dur * 1000);
+    bench.start();
+    pummel();
+  });
+
+  function pummel() {
+    var req = http.request(options, function(res) {
+      nreqs++;
+      pummel();  // Line up next request.
+      res.resume();
+    });
+    if (conf.method === 'write') {
+      req.write(chunk, encoding);
+      req.end();
+    } else {
+      req.end(chunk, encoding);
+    }
+  }
+
+  function done() {
+    bench.end(nreqs);
+  }
+}
diff --git a/lib/http.js b/lib/http.js
index 4a4fe94f3e..bcde516dae 100644
--- a/lib/http.js
+++ b/lib/http.js
@@ -782,12 +782,28 @@ OutgoingMessage.prototype.write = function(chunk, encoding) {
 
   if (chunk.length === 0) return false;
 
+  // TODO(bnoordhuis) Temporary optimization hack, remove in v0.11. We only
+  // want to convert the buffer when we're sending:
+  //
+  //   a) Transfer-Encoding chunks, because it lets us pack the chunk header
+  //      and the chunk into a single write(), or
+  //
+  //   b) the first chunk of a fixed-length request, because it lets us pack
+  //      the request headers and the chunk into a single write().
+  //
+  // Converting to strings is expensive, CPU-wise, but reducing the number
+  // of write() calls more than makes up for that because we're dramatically
+  // reducing the number of TCP roundtrips.
+  if (chunk instanceof Buffer && (this.chunkedEncoding || !this._headerSent)) {
+    chunk = chunk.toString('binary');
+    encoding = 'binary';
+  }
+
   var len, ret;
   if (this.chunkedEncoding) {
     if (typeof(chunk) === 'string' &&
         encoding !== 'hex' &&
-        encoding !== 'base64' &&
-        encoding !== 'binary') {
+        encoding !== 'base64') {
       len = Buffer.byteLength(chunk, encoding);
       chunk = len.toString(16) + CRLF + chunk + CRLF;
       ret = this._send(chunk, encoding);