diff --git a/event_iocp.c b/event_iocp.c
new file mode 100644
index 0000000..9648366
--- /dev/null
+++ b/event_iocp.c
@@ -0,0 +1,293 @@
+/*
+ * Copyright (c) 2009-2012 Niels Provos, Nick Mathewson
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _WIN32_WINNT
+/* Minimum required for InitializeCriticalSectionAndSpinCount */
+#define _WIN32_WINNT 0x0403
+#endif
+#include <winsock2.h>
+#include <windows.h>
+#include <process.h>
+#include <stdio.h>
+#include <mswsock.h>
+
+#include "event2/util.h"
+#include "util-internal.h"
+#include "iocp-internal.h"
+#include "log-internal.h"
+#include "mm-internal.h"
+#include "event-internal.h"
+#include "evthread-internal.h"
+
+#define NOTIFICATION_KEY ((ULONG_PTR)-1)
+
+void
+event_overlapped_init(struct event_overlapped *o, iocp_callback cb)
+{
+	memset(o, 0, sizeof(struct event_overlapped));
+	o->cb = cb;
+}
+
+static void
+handle_entry(OVERLAPPED *o, ULONG_PTR completion_key, DWORD nBytes, int ok)
+{
+	struct event_overlapped *eo =
+	    EVUTIL_UPCAST(o, struct event_overlapped, overlapped);
+	eo->cb(eo, completion_key, nBytes, ok);
+}
+
+static void
+loop(void *_port)
+{
+	struct event_iocp_port *port = _port;
+	long ms = port->ms;
+	HANDLE p = port->port;
+
+	if (ms <= 0)
+		ms = INFINITE;
+
+	while (1) {
+		OVERLAPPED *overlapped=NULL;
+		ULONG_PTR key=0;
+		DWORD bytes=0;
+		int ok = GetQueuedCompletionStatus(p, &bytes, &key,
+			&overlapped, ms);
+		EnterCriticalSection(&port->lock);
+		if (port->shutdown) {
+			if (--port->n_live_threads == 0)
+				ReleaseSemaphore(port->shutdownSemaphore, 1,
+						NULL);
+			LeaveCriticalSection(&port->lock);
+			return;
+		}
+		LeaveCriticalSection(&port->lock);
+
+		if (key != NOTIFICATION_KEY && overlapped)
+			handle_entry(overlapped, key, bytes, ok);
+		else if (!overlapped)
+			break;
+	}
+	event_warnx("GetQueuedCompletionStatus exited with no event.");
+	EnterCriticalSection(&port->lock);
+	if (--port->n_live_threads == 0)
+		ReleaseSemaphore(port->shutdownSemaphore, 1, NULL);
+	LeaveCriticalSection(&port->lock);
+}
+
+int
+event_iocp_port_associate(struct event_iocp_port *port, evutil_socket_t fd,
+    ev_uintptr_t key)
+{
+	HANDLE h;
+	h = CreateIoCompletionPort((HANDLE)fd, port->port, key, port->n_threads);
+	if (!h)
+		return -1;
+	return 0;
+}
+
+static void *
+get_extension_function(SOCKET s, const GUID *which_fn)
+{
+	void *ptr = NULL;
+	DWORD bytes=0;
+	WSAIoctl(s, SIO_GET_EXTENSION_FUNCTION_POINTER,
+	    (GUID*)which_fn, sizeof(*which_fn),
+	    &ptr, sizeof(ptr),
+	    &bytes, NULL, NULL);
+
+	/* No need to detect errors here: if ptr is set, then we have a good
+	   function pointer.  Otherwise, we should behave as if we had no
+	   function pointer.
+	*/
+	return ptr;
+}
+
+/* Mingw doesn't have these in its mswsock.h.  The values are copied from
+   wine.h.   Perhaps if we copy them exactly, the cargo will come again.
+*/
+#ifndef WSAID_ACCEPTEX
+#define WSAID_ACCEPTEX \
+	{0xb5367df1,0xcbac,0x11cf,{0x95,0xca,0x00,0x80,0x5f,0x48,0xa1,0x92}}
+#endif
+#ifndef WSAID_CONNECTEX
+#define WSAID_CONNECTEX \
+	{0x25a207b9,0xddf3,0x4660,{0x8e,0xe9,0x76,0xe5,0x8c,0x74,0x06,0x3e}}
+#endif
+#ifndef WSAID_GETACCEPTEXSOCKADDRS
+#define WSAID_GETACCEPTEXSOCKADDRS \
+	{0xb5367df2,0xcbac,0x11cf,{0x95,0xca,0x00,0x80,0x5f,0x48,0xa1,0x92}}
+#endif
+
+static int extension_fns_initialized = 0;
+
+static void
+init_extension_functions(struct win32_extension_fns *ext)
+{
+	const GUID acceptex = WSAID_ACCEPTEX;
+	const GUID connectex = WSAID_CONNECTEX;
+	const GUID getacceptexsockaddrs = WSAID_GETACCEPTEXSOCKADDRS;
+	SOCKET s = socket(AF_INET, SOCK_STREAM, 0);
+	if (s == INVALID_SOCKET)
+		return;
+	ext->AcceptEx = get_extension_function(s, &acceptex);
+	ext->ConnectEx = get_extension_function(s, &connectex);
+	ext->GetAcceptExSockaddrs = get_extension_function(s,
+	    &getacceptexsockaddrs);
+	closesocket(s);
+
+	extension_fns_initialized = 1;
+}
+
+static struct win32_extension_fns the_extension_fns;
+
+const struct win32_extension_fns *
+event_get_win32_extension_fns(void)
+{
+	return &the_extension_fns;
+}
+
+#define N_CPUS_DEFAULT 2
+
+struct event_iocp_port *
+event_iocp_port_launch(int n_cpus)
+{
+	struct event_iocp_port *port;
+	int i;
+
+	if (!extension_fns_initialized)
+		init_extension_functions(&the_extension_fns);
+
+	if (!(port = mm_calloc(1, sizeof(struct event_iocp_port))))
+		return NULL;
+
+	if (n_cpus <= 0)
+		n_cpus = N_CPUS_DEFAULT;
+	port->n_threads = n_cpus * 2;
+	port->threads = mm_calloc(port->n_threads, sizeof(HANDLE));
+	if (!port->threads)
+		goto err;
+
+	port->port = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0,
+			n_cpus);
+	port->ms = -1;
+	if (!port->port)
+		goto err;
+
+	port->shutdownSemaphore = CreateSemaphore(NULL, 0, 1, NULL);
+	if (!port->shutdownSemaphore)
+		goto err;
+
+	for (i=0; i<port->n_threads; ++i) {
+		ev_uintptr_t th = _beginthread(loop, 0, port);
+		if (th == (ev_uintptr_t)-1)
+			goto err;
+		port->threads[i] = (HANDLE)th;
+		++port->n_live_threads;
+	}
+
+	InitializeCriticalSectionAndSpinCount(&port->lock, 1000);
+
+	return port;
+err:
+	if (port->port)
+		CloseHandle(port->port);
+	if (port->threads)
+		mm_free(port->threads);
+	if (port->shutdownSemaphore)
+		CloseHandle(port->shutdownSemaphore);
+	mm_free(port);
+	return NULL;
+}
+
+static void
+_event_iocp_port_unlock_and_free(struct event_iocp_port *port)
+{
+	DeleteCriticalSection(&port->lock);
+	CloseHandle(port->port);
+	CloseHandle(port->shutdownSemaphore);
+	mm_free(port->threads);
+	mm_free(port);
+}
+
+static int
+event_iocp_notify_all(struct event_iocp_port *port)
+{
+	int i, r, ok=1;
+	for (i=0; i<port->n_threads; ++i) {
+		r = PostQueuedCompletionStatus(port->port, 0, NOTIFICATION_KEY,
+		    NULL);
+		if (!r)
+			ok = 0;
+	}
+	return ok ? 0 : -1;
+}
+
+int
+event_iocp_shutdown(struct event_iocp_port *port, long waitMsec)
+{
+	DWORD ms = INFINITE;
+	int n;
+
+	EnterCriticalSection(&port->lock);
+	port->shutdown = 1;
+	LeaveCriticalSection(&port->lock);
+	event_iocp_notify_all(port);
+
+	if (waitMsec >= 0)
+		ms = waitMsec;
+
+	WaitForSingleObject(port->shutdownSemaphore, ms);
+	EnterCriticalSection(&port->lock);
+	n = port->n_live_threads;
+	LeaveCriticalSection(&port->lock);
+	if (n == 0) {
+		_event_iocp_port_unlock_and_free(port);
+		return 0;
+	} else {
+		return -1;
+	}
+}
+
+int
+event_iocp_activate_overlapped(
+    struct event_iocp_port *port, struct event_overlapped *o,
+    ev_uintptr_t key, ev_uint32_t n)
+{
+	BOOL r;
+
+	r = PostQueuedCompletionStatus(port->port, n, key, &o->overlapped);
+	return (r==0) ? -1 : 0;
+}
+
+struct event_iocp_port *
+event_base_get_iocp(struct event_base *base)
+{
+#ifdef WIN32
+	return base->iocp;
+#else
+	return NULL;
+#endif
+}