diff --git a/tornado/curl_httpclient.py b/tornado/curl_httpclient.py
index b8fd4052..53824c84 100644
--- a/tornado/curl_httpclient.py
+++ b/tornado/curl_httpclient.py
@@ -271,7 +271,7 @@ def _curl_create(max_simultaneous_connections=None):
 
 
 def _curl_setup_request(curl, request, buffer, headers):
-    curl.setopt(pycurl.URL, request.url)
+    curl.setopt(pycurl.URL, utf8(request.url))
 
     # libcurl's magic "Expect: 100-continue" behavior causes delays
     # with servers that don't support it (which include, among others,
diff --git a/tornado/httpclient.py b/tornado/httpclient.py
index a6ad4fa1..1280a47d 100644
--- a/tornado/httpclient.py
+++ b/tornado/httpclient.py
@@ -54,9 +54,11 @@ class HTTPClient(object):
         except httpclient.HTTPError, e:
             print "Error:", e
     """
-    def __init__(self):
+    def __init__(self, async_client_class=None):
         self._io_loop = IOLoop()
-        self._async_client = AsyncHTTPClient(self._io_loop)
+        if async_client_class is None:
+            async_client_class = AsyncHTTPClient
+        self._async_client = async_client_class(self._io_loop)
         self._response = None
         self._closed = False
 
diff --git a/tornado/test/httpserver_test.py b/tornado/test/httpserver_test.py
index 03634852..5eb46208 100644
--- a/tornado/test/httpserver_test.py
+++ b/tornado/test/httpserver_test.py
@@ -118,7 +118,8 @@ class HTTPConnectionTest(AsyncHTTPTestCase, LogTrapTestCase):
         return Application(self.get_handlers())
 
     def raw_fetch(self, headers, body):
-        conn = RawRequestHTTPConnection(self.io_loop, self.http_client,
+        client = SimpleAsyncHTTPClient(self.io_loop)
+        conn = RawRequestHTTPConnection(self.io_loop, client,
                                         httpclient.HTTPRequest(self.get_url("/")),
                                         None, self.stop,
                                         1024*1024)
@@ -127,6 +128,7 @@ class HTTPConnectionTest(AsyncHTTPTestCase, LogTrapTestCase):
                            [utf8("Content-Length: %d\r\n" % len(body))]) +
             b("\r\n") + body)
         response = self.wait()
+        client.close()
         response.rethrow()
         return response
 
diff --git a/tornado/test/process_test.py b/tornado/test/process_test.py
index 91f75b0a..de9ae523 100644
--- a/tornado/test/process_test.py
+++ b/tornado/test/process_test.py
@@ -9,6 +9,7 @@ from tornado.httpserver import HTTPServer
 from tornado.ioloop import IOLoop
 from tornado.netutil import bind_sockets
 from tornado.process import fork_processes, task_id
+from tornado.simple_httpclient import SimpleAsyncHTTPClient
 from tornado.testing import LogTrapTestCase, get_unused_port
 from tornado.web import RequestHandler, Application
 
@@ -72,7 +73,11 @@ class ProcessTest(LogTrapTestCase):
                 signal.alarm(5)
                 self.assertEqual(id, task_id())
                 for sock in sockets: sock.close()
-                client = HTTPClient()
+                # Always use SimpleAsyncHTTPClient here; the curl
+                # version appears to get confused sometimes if the
+                # connection gets closed before it's had a chance to
+                # switch from writing mode to reading mode.
+                client = HTTPClient(SimpleAsyncHTTPClient)
 
                 def fetch(url, fail_ok=False):
                     try:
diff --git a/tornado/test/simple_httpclient_test.py b/tornado/test/simple_httpclient_test.py
index 7b7eb19e..a65c8c68 100644
--- a/tornado/test/simple_httpclient_test.py
+++ b/tornado/test/simple_httpclient_test.py
@@ -55,6 +55,10 @@ class NoContentHandler(RequestHandler):
         self.set_status(204)
 
 class SimpleHTTPClientTestCase(AsyncHTTPTestCase, LogTrapTestCase):
+    def setUp(self):
+        super(SimpleHTTPClientTestCase, self).setUp()
+        self.http_client = SimpleAsyncHTTPClient(self.io_loop)
+
     def get_app(self):
         # callable objects to finish pending /trigger requests
         self.triggers = collections.deque()
diff --git a/tox.ini b/tox.ini
index 96e24276..30a78088 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,7 @@
 [tox]
 # "-full" variants include optional dependencies, to ensure
 # that things work both in a bare install and with all the extras.
-envlist = py27-full, py25-full, py32, pypy, py25, py26, py26-full, py27
+envlist = py27-full, py27-curl, py25-full, py32, pypy, py25, py26, py26-full, py27
 [testenv]
 commands = python -m tornado.test.runtests {posargs:}
 
@@ -52,6 +52,17 @@ deps =
      pycurl
      twisted==11.0.0
 
+[testenv:py27-curl]
+# Same as py27-full, but runs the tests with curl_httpclient by default.
+# Note that httpclient_test is always run with both client implementations;
+# this flag controls which client all the other tests use.
+basepython = python2.7
+deps =
+     MySQL-python
+     pycurl
+     twisted==11.0.0
+commands = python -m tornado.test.runtests --httpclient=tornado.curl_httpclient.CurlAsyncHTTPClient {posargs:}
+
 # No pypy-full yet: pycurl doesn't build with pypy, and installing
 # twisted under pypy takes a *very* long time.  MySQL-python builds with
 # pypy, but doesn't work.