diff --git a/gerrit_upload.py b/gerrit_upload.py
index f8dccdc5..32451408 100755
--- a/gerrit_upload.py
+++ b/gerrit_upload.py
@@ -75,6 +75,7 @@ def UploadBundle(project,
                  dest_branch,
                  src_branch,
                  bases,
+                 replace_changes = None,
                  save_cookies=True):
 
   srv = _GetRpcServer(email, server, save_cookies)
@@ -113,6 +114,10 @@ def UploadBundle(project,
         req.dest_branch = str(dest_branch)
         for c in revlist:
           req.contained_object.append(c)
+        for change_id,commit_id in replace_changes.iteritems():
+          r = req.replace.add()
+          r.change_id = change_id
+          r.object_id = commit_id
       else:
         req = UploadBundleContinue()
         req.bundle_id = bundle_id
@@ -148,6 +153,10 @@ def UploadBundle(project,
         elif rsp.status_code == UploadBundleResponse.UNAUTHORIZED_USER:
           reason = ('Unauthorized user.  Visit http://%s/hello to sign up.'
                     % server)
+        elif rsp.status_code == UploadBundleResponse.UNKNOWN_CHANGE:
+          reason = 'invalid change id'
+        elif rsp.status_code == UploadBundleResponse.CHANGE_CLOSED:
+          reason = 'one or more changes are closed'
         else:
           reason = 'unknown error ' + str(rsp.status_code)
         raise UploadError(reason)
diff --git a/project.py b/project.py
index 1e25c2c9..39550335 100644
--- a/project.py
+++ b/project.py
@@ -104,6 +104,7 @@ class ReviewableBranch(object):
     self.project = project
     self.branch = branch
     self.base = base
+    self.replace_changes = None
 
   @property
   def name(self):
@@ -123,6 +124,16 @@ class ReviewableBranch(object):
         '--')
     return self._commit_cache
 
+  @property
+  def unabbrev_commits(self):
+    r = dict()
+    for commit in self.project.bare_git.rev_list(
+        not_rev(self.base),
+        R_HEADS + self.name,
+        '--'):
+      r[commit[0:8]] = commit
+    return r
+
   @property
   def date(self):
     return self.project.bare_git.log(
@@ -132,7 +143,8 @@ class ReviewableBranch(object):
       '--')
 
   def UploadForReview(self):
-    self.project.UploadForReview(self.name)
+    self.project.UploadForReview(self.name,
+                                 self.replace_changes)
 
   @property
   def tip_url(self):
@@ -444,7 +456,7 @@ class Project(object):
         return rb
     return None
 
-  def UploadForReview(self, branch=None):
+  def UploadForReview(self, branch=None, replace_changes=None):
     """Uploads the named branch for code review.
     """
     if branch is None:
@@ -482,7 +494,8 @@ class Project(object):
                    dest_project = branch.remote.projectname,
                    dest_branch = dest_branch,
                    src_branch = R_HEADS + branch.name,
-                   bases = base_list)
+                   bases = base_list,
+                   replace_changes = replace_changes)
     except proto_client.ClientLoginError:
       raise UploadError('Login failure')
     except urllib2.HTTPError, e:
diff --git a/subcmds/upload.py b/subcmds/upload.py
index 9018455f..11f035d7 100644
--- a/subcmds/upload.py
+++ b/subcmds/upload.py
@@ -29,7 +29,7 @@ class Upload(InteractiveCommand):
   common = True
   helpSummary = "Upload changes for code review"
   helpUsage="""
-%prog [<project>]...
+%prog {[<project>]... | --replace <project>}
 """
   helpDescription = """
 The '%prog' command is used to send changes to the Gerrit code
@@ -46,6 +46,11 @@ no projects are specified, '%prog' will search for uploadable
 changes in all projects listed in the manifest.
 """
 
+  def _Options(self, p):
+    p.add_option('--replace',
+                 dest='replace', action='store_true',
+                 help='Upload replacement patchesets from this branch')
+
   def _SingleBranch(self, branch):
     project = branch.project
     name = branch.name
@@ -129,6 +134,50 @@ changes in all projects listed in the manifest.
       _die("nothing uncommented for upload")
     self._UploadAndReport(todo)
 
+  def _ReplaceBranch(self, project):
+    branch = project.CurrentBranch
+    if not branch:
+      print >>sys.stdout, "no branches ready for upload"
+      return
+    branch = project.GetUploadableBranch(branch)
+    if not branch:
+      print >>sys.stdout, "no branches ready for upload"
+      return
+
+    script = []
+    script.append('# Replacing from branch %s' % branch.name)
+    for commit in branch.commits:
+      script.append('[      ] %s' % commit)
+    script.append('')
+    script.append('# Insert change numbers in the brackets to add a new patch set.')
+    script.append('# To create a new change record, leave the brackets empty.')
+
+    script = Editor.EditString("\n".join(script)).split("\n")
+
+    change_re = re.compile(r'^\[\s*(\d{1,})\s*\]\s*([0-9a-f]{1,}) .*$')
+    to_replace = dict()
+    full_hashes = branch.unabbrev_commits
+
+    for line in script:
+      m = change_re.match(line)
+      if m:
+        f = m.group(2)
+        try:
+          f = full_hashes[f]
+        except KeyError:
+          print 'fh = %s' % full_hashes
+          print >>sys.stderr, "error: commit %s not found" % f
+          sys.exit(1)
+        to_replace[m.group(1)] = f
+
+    if not to_replace:
+      print >>sys.stderr, "error: no replacements specified"
+      print >>sys.stderr, "       use 'repo upload' without --replace"
+      sys.exit(1)
+
+    branch.replace_changes = to_replace
+    self._UploadAndReport([branch])
+
   def _UploadAndReport(self, todo):
     have_errors = False
     for branch in todo:
@@ -168,6 +217,14 @@ changes in all projects listed in the manifest.
     project_list = self.GetProjects(args)
     pending = []
 
+    if opt.replace:
+      if len(project_list) != 1:
+        print >>sys.stderr, \
+              'error: --replace requires exactly one project'
+        sys.exit(1)
+      self._ReplaceBranch(project_list[0])
+      return
+
     for project in project_list:
       avail = project.GetUploadableBranches()
       if avail: