diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -1249,15 +1249,35 @@
         pass
     return baseset(datarepr=('<max %r, %r>', subset, os))
 
-@predicate('merge()', safe=True)
+@predicate('merge([withbranch])', safe=True)
 def merge(repo, subset, x):
-    """Changeset is a merge changeset.
-    """
+    """Changeset is a merge changeset
+
+    All merge revisions are returned by default. If a "withbranch"
+    pattern is provided only merges with (i.e. whose second parent
+    belongs to) those branches that match the pattern will be returned.
+    The simplest pattern is the name of a single branch. It is also
+    possible to specify a regular expression by starting the pattern
+    with "re:". This can be used to match more than one branch
+    (e.g. "re:branch1|branch2").
+    """
+    cl = repo.changelog
+    # matchfn is a function that returns true when a revision is a merge
+    matchfn = lambda r: cl.parentrevs(r)[1] != -1
+
     # i18n: "merge" is a keyword
-    getargs(x, 0, 0, _("merge takes no arguments"))
-    cl = repo.changelog
-    return subset.filter(lambda r: cl.parentrevs(r)[1] != -1,
-                         condrepr='<merge>')
+    args = getargsdict(x, 'merge', 'withbranch')
+    if 'withbranch' in args:
+        withbranch = getstring(args['withbranch'],
+                               _('withbranch argument must be a string'))
+        kind, branchname, branchmatcher = stringutil.stringmatcher(withbranch)
+        if branchname:
+            # create the function that will filter the subset
+            # is a merge and the second parent belongs to a branch that
+            # matches the withbranch pattern (which can be a literal or a regex)
+            matchfn = lambda r: (cl.parentrevs(r)[1] != -1
+                                 and branchmatcher(repo[r].p2().branch()))
+    return subset.filter(matchfn, condrepr='<merge>')
 
 @predicate('branchpoint()', safe=True)
 def branchpoint(repo, subset, x):
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -1743,8 +1743,15 @@
 Test section lookup
 
   $ hg help revset.merge
-      "merge()"
-        Changeset is a merge changeset.
+      "merge([withbranch])"
+        Changeset is a merge changeset
+  
+        All merge revisions are returned by default. If a "withbranch" pattern
+        is provided only merges with (i.e. whose second parent belongs to) those
+        branches that match the pattern will be returned. The simplest pattern
+        is the name of a single branch. It is also possible to specify a regular
+        expression by starting the pattern with "re:". This can be used to match
+        more than one branch (e.g. "re:branch1|branch2").
   
   $ hg help glossary.dag
       DAG
diff --git a/tests/test-revset.t b/tests/test-revset.t
--- a/tests/test-revset.t
+++ b/tests/test-revset.t
@@ -2954,3 +2954,82 @@
   * set:
   <baseset+ [0]>
   0
+
+test the merge() revset parameters
+
+create a few merge revisions to test merge() parameters
+  $ hg up 9
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ echo a > a
+  $ hg branch --force ".a.b.c."
+  marked working directory as branch .a.b.c.
+  $ hg add a
+  $ hg commit -m "added a"
+  created new head
+  $ hg merge 7
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg commit -m "same branch merge 1"
+  $ hg up 10
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ echo a2 > a
+  $ hg commit -m "changed a to a2"
+  created new head
+  $ hg up 11
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge 12
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg commit -m "same branch merge 2"
+  $ echo a3 > a
+  $ hg commit -m "changed a to a3"
+  $ hg up 12
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg branch --force "_a_b_c_"
+  marked working directory as branch _a_b_c_
+  $ hg merge 14
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg commit -m "same branch merge 3 (both parents on same branch while merge is on another branch)"
+  created new head
+  $ hg up 14
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ echo a4 > a
+  $ hg commit -m "changed a to a4"
+  $ hg up 15
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge 16
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg commit -m "different branch merge 1"
+  $ hg up 16
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ echo a5 > a
+  $ hg branch --force "_a_b_c_"
+  marked working directory as branch _a_b_c_
+  $ hg commit -m "changed a to a5"
+  created new head
+  $ hg up 17
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg merge 18
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ hg commit -m "different branch merge 2"
+
+show merges with a particular branch
+  $ log 'merge(.a.b.c.)'
+  11
+  13
+  15
+  17
+  $ log 'merge(-a-b-c-)'
+  6
+
+show merges with multiple branches using a regex
+  $ log 'merge("re:.a.b.c.")'
+  6
+  11
+  13
+  15
+  17
+  19