diff --git a/mercurial/hgweb/protocol.py b/mercurial/hgweb/protocol.py
--- a/mercurial/hgweb/protocol.py
+++ b/mercurial/hgweb/protocol.py
@@ -45,6 +45,11 @@ class webproto(wireproto.abstractserverp
         return [data[k] for k in keys]
     def _args(self):
         args = self.req.form.copy()
+        postlen = int(self.req.env.get('HTTP_X_HGARGS_POST', 0))
+        if postlen:
+            args.update(cgi.parse_qs(
+                self.req.read(postlen), keep_blank_values=True))
+            return args
         chunks = []
         i = 1
         while True:
diff --git a/mercurial/httppeer.py b/mercurial/httppeer.py
--- a/mercurial/httppeer.py
+++ b/mercurial/httppeer.py
@@ -97,7 +97,22 @@ class httppeer(wireproto.wirepeer):
         self.ui.debug("sending %s command\n" % cmd)
         q = [('cmd', cmd)]
         headersize = 0
-        if True:
+        # Important: don't use self.capable() here or else you end up
+        # with infinite recursion when trying to look up capabilities
+        # for the first time.
+        postargsok = self.caps is not None and 'httppostargs' in self.caps
+        # TODO: support for httppostargs when data is a file-like
+        # object rather than a basestring
+        canmungedata = not data or isinstance(data, basestring)
+        if postargsok and canmungedata:
+            strargs = urllib.urlencode(sorted(args.items()))
+            if strargs:
+                if not data:
+                    data = strargs
+                elif isinstance(data, basestring):
+                    data = strargs + data
+                headers['X-HgArgs-Post'] = len(strargs)
+        else:
             if len(args) > 0:
                 httpheader = self.capable('httpheader')
                 if httpheader:
diff --git a/mercurial/wireproto.py b/mercurial/wireproto.py
--- a/mercurial/wireproto.py
+++ b/mercurial/wireproto.py
@@ -688,6 +688,8 @@ def _capabilities(repo, proto):
     caps.append('unbundle=%s' % ','.join(changegroupmod.bundlepriority))
     caps.append(
         'httpheader=%d' % repo.ui.configint('server', 'maxhttpheaderlen', 1024))
+    if repo.ui.configbool('experimental', 'httppostargs', False):
+        caps.append('httppostargs')
     return caps
 
 # If you are writing an extension and consider wrapping this function. Wrap
diff --git a/tests/test-wireproto.t b/tests/test-wireproto.t
--- a/tests/test-wireproto.t
+++ b/tests/test-wireproto.t
@@ -19,7 +19,9 @@ Local:
 
 HTTP:
 
-  $ hg serve -R repo -p $HGPORT -d --pid-file=hg1.pid -E error.log -A access.log
+  $ hg  serve -R repo -p $HGPORT -d --pid-file=hg1.pid \
+  >   -E error.log -A access.log \
+  >   --config experimental.httppostargs=yes
   $ cat hg1.pid >> $DAEMON_PIDS
 
   $ hg debugwireargs http://localhost:$HGPORT/ un deux trois quatre
@@ -37,6 +39,61 @@ HTTP:
   $ cat error.log
   $ cat access.log
   * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:39 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:39 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:43 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:43 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:27 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:27 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:17 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:17 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:17 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:17 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:1033 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:1033 (glob)
+
+HTTP without args-in-POST:
+  $ hg serve -R repo -p $HGPORT1 -d --pid-file=hg1.pid -E error.log -A access.log
+  $ cat hg1.pid >> $DAEMON_PIDS
+
+  $ hg debugwireargs http://localhost:$HGPORT1/ un deux trois quatre
+  un deux trois quatre None
+  $ hg debugwireargs http://localhost:$HGPORT1/ \ un deux trois\  qu\ \ atre
+   un deux trois  qu  atre None
+  $ hg debugwireargs http://localhost:$HGPORT1/ eins zwei --four vier
+  eins zwei None vier None
+  $ hg debugwireargs http://localhost:$HGPORT1/ eins zwei
+  eins zwei None None None
+  $ hg debugwireargs http://localhost:$HGPORT1/ eins zwei --five fuenf
+  eins zwei None None None
+  $ hg debugwireargs http://localhost:$HGPORT1/ un deux trois onethousandcharactersxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+  un deux trois onethousandcharactersxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx None
+  $ cat error.log
+  $ cat access.log
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:39 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:39 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:43 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:43 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:27 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:27 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:17 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:17 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:17 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:17 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:1033 (glob)
+  * - - [*] "POST /?cmd=debugwireargs HTTP/1.1" 200 - x-hgargs-post:1033 (glob)
+  * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)
   * - - [*] "GET /?cmd=debugwireargs HTTP/1.1" 200 - x-hgarg-1:four=quatre&one=un&three=trois&two=deux (glob)
   * - - [*] "GET /?cmd=debugwireargs HTTP/1.1" 200 - x-hgarg-1:four=quatre&one=un&three=trois&two=deux (glob)
   * - - [*] "GET /?cmd=capabilities HTTP/1.1" 200 - (glob)