diff -r f8ee36489d3c -r c8e4c6e03957 src/topic/__init__.py
--- a/src/topic/__init__.py	Mon Mar 14 17:09:02 2016 +0000
+++ b/src/topic/__init__.py	Mon Mar 14 17:37:39 2016 +0000
@@ -38,6 +38,7 @@
 from . import constants
 from . import revset as topicrevset
 from . import destination
+from . import stack
 from . import topicmap
 from . import discovery
 
@@ -165,9 +166,15 @@
 @command('topics [TOPIC]', [
     ('', 'clear', False, 'clear active topic if any'),
     ('', 'change', '', 'revset of existing revisions to change topic'),
+    ('l', 'list', False, 'show the stack of changeset in the topic'),
 ])
-def topics(ui, repo, topic='', clear=False, change=None):
+def topics(ui, repo, topic='', clear=False, change=None, list=False):
     """View current topic, set current topic, or see all topics."""
+    if list:
+        if clear or change:
+            raise error.Abort(_("cannot use --clear or --change with --list"))
+        return stack.showstack(ui, repo, topic)
+
     if change:
         if not obsolete.isenabled(repo, obsolete.createmarkersopt):
             raise error.Abort(_('must have obsolete enabled to use --change'))