diff -r ef4d1846c09a Lib/imaplib.py
--- a/Lib/imaplib.py	Tue Jan 03 22:31:23 2012 +0200
+++ b/Lib/imaplib.py	Tue Jan 03 23:22:17 2012 +0200
@@ -538,7 +538,7 @@
     def _CRAM_MD5_AUTH(self, challenge):
         """ Authobject to use with CRAM-MD5 authentication. """
         import hmac
-        return self.user + " " + hmac.HMAC(self.password, challenge).hexdigest()
+        return self.user + " " + hmac.HMAC(self.password.encode(), challenge).hexdigest()
 
 
     def logout(self):
diff -r ef4d1846c09a Lib/test/test_imaplib.py
--- a/Lib/test/test_imaplib.py	Tue Jan 03 22:31:23 2012 +0200
+++ b/Lib/test/test_imaplib.py	Tue Jan 03 23:22:17 2012 +0200
@@ -242,6 +242,48 @@
             self.assertRaises(imaplib.IMAP4.abort,
                               self.imap_class, *server.server_address)
 
+    @reap_threads
+    def test_login_cram_md5(self):
+        """ Tests CRAM-MD5 authentication and logging out """
+
+        class AuthHandler(SimpleIMAPHandler):
+
+            def cmd_CAPABILITY(self, tag, args):
+                self._send(b'* CAPABILITY IMAP4rev1 LOGINDISABLED AUTH=CRAM-MD5\r\n')
+                self._send('{} OK Capability completed.\r\n'.format(tag).encode('ASCII'))
+
+            def cmd_AUTHENTICATE(self, tag, args):
+                self._send(b'+ PDE4OTYuNjk3MTcwOTUyQHBvc3RvZmZpY2UucmVzdG9uLm1jaS5uZXQ+\r\n')
+                self._contcmd = self._cmd_AUTHENTICATE_CONT
+
+            def _cmd_AUTHENTICATE_CONT(self, tag, args):
+                if args == b"dGltIGI5MTNhNjAyYzdlZGE3YTQ5NWI0ZTZlNzMzNGQzODkw\r\n":
+                    self._send('{} OK CRAM-MD5 authentication successful\r\n'
+                               .format(tag).encode('ASCII'))
+                else:
+                    self._send('{} NO No access\r\n'.format(tag).encode('ASCII'))
+                self._contcmd = None
+
+            def cmd_LOGOUT(self, tag, args):
+                self._send(b'* BYE Logging out\r\n')
+                self._send('{} OK Logout completed.\r\n'.format(tag).encode('ASCII'))
+
+        with self.reaped_server(AuthHandler) as server:
+            try:
+                client = self.imap_class(*server.server_address)
+            except imaplib.IMAP4.abort:
+                self.fail("IMAP4 connection failed")
+
+            self.assertTrue('AUTH=CRAM-MD5' in client.capabilities)
+
+            try:
+                ret, data = client.login_cram_md5("tim", "tanstaaftanstaaf")
+                self.assertEqual(ret, "OK")
+            except imaplib.error:
+                self.fail("CRAM-MD5 authentication failed")
+
+            ret, data = client.logout()
+            self.assertEqual(ret, "BYE")
 
 
 class ThreadedNetworkedTests(BaseThreadedNetworkedTests):