diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -298,9 +298,18 @@ def children(repo, subset, x):
     return [r for r in subset if r in cs]
 
 def branch(repo, subset, x):
-    """``branch(set)``
-    All changesets belonging to the branches of changesets in set.
+    """``branch(string or set)``
+    All changesets belonging to the given branch or the branches of the given
+    changesets.
     """
+    try:
+        b = getstring(x, '')
+        if b in repo.branchmap():
+            return [r for r in subset if repo[r].branch() == b]
+    except error.ParseError:
+        # not a string, but another revspec, e.g. tip()
+        pass
+
     s = getset(repo, range(len(repo)), x)
     b = set()
     for r in s:
diff --git a/tests/test-branch-tag-confict.t b/tests/test-branch-tag-confict.t
new file mode 100644
--- /dev/null
+++ b/tests/test-branch-tag-confict.t
@@ -0,0 +1,62 @@
+Initial setup.
+
+  $ hg init repo
+  $ cd repo
+  $ touch thefile
+  $ hg ci -A -m 'Initial commit.'
+  adding thefile
+
+Create a tag.
+
+  $ hg tag branchortag
+
+Create a branch with the same name as the tag.
+
+  $ hg branch branchortag
+  marked working directory as branch branchortag
+  $ hg ci -m 'Create a branch with the same name as a tag.'
+
+This is what we have:
+
+  $ hg log
+  changeset:   2:02b1af9b58c2
+  branch:      branchortag
+  tag:         tip
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     Create a branch with the same name as a tag.
+  
+  changeset:   1:2635c45ca99b
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     Added tag branchortag for changeset f57387372b5d
+  
+  changeset:   0:f57387372b5d
+  tag:         branchortag
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     Initial commit.
+  
+Update to the tag:
+
+  $ hg up 'tag(branchortag)'
+  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ hg parents
+  changeset:   0:f57387372b5d
+  tag:         branchortag
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     Initial commit.
+  
+Updating to the branch:
+
+  $ hg up 'branch(branchortag)'
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg parents
+  changeset:   2:02b1af9b58c2
+  branch:      branchortag
+  tag:         tip
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     Create a branch with the same name as a tag.
+