diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -1597,10 +1597,12 @@ def show_changeset(ui, repo, opts, buffe
         raise error.Abort(inst.args[0])
     return t
 
-def showmarker(ui, marker):
+def showmarker(ui, marker, index=None):
     """utility function to display obsolescence marker in a readable way
 
     To be used by debug function."""
+    if index is not None:
+        ui.write("%i " % index)
     ui.write(hex(marker.precnode()))
     for repl in marker.succnodes():
         ui.write(' ')
diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -3029,6 +3029,7 @@ def debuglocks(ui, repo, **opts):
          ('', 'record-parents', False,
           _('record parent information for the precursor')),
          ('r', 'rev', [], _('display markers relevant to REV')),
+         ('', 'index', False, _('display index of the marker')),
         ] + commitopts2,
          _('[OBSOLETED [REPLACEMENT ...]]'))
 def debugobsolete(ui, repo, precursor=None, *successors, **opts):
@@ -3091,8 +3092,9 @@ def debugobsolete(ui, repo, precursor=No
         else:
             markers = obsolete.getmarkers(repo)
 
-        for m in markers:
-            cmdutil.showmarker(ui, m)
+        for i, m in enumerate(markers):
+            ind = i if opts.get('index') else None
+            cmdutil.showmarker(ui, m, index=ind)
 
 @command('debugpathcomplete',
          [('f', 'full', None, _('complete an entire path')),
diff --git a/tests/test-completion.t b/tests/test-completion.t
--- a/tests/test-completion.t
+++ b/tests/test-completion.t
@@ -261,7 +261,7 @@ Show all commands + options
   debuglocks: force-lock, force-wlock
   debugmergestate: 
   debugnamecomplete: 
-  debugobsolete: flags, record-parents, rev, date, user
+  debugobsolete: flags, record-parents, rev, index, date, user
   debugpathcomplete: full, normal, added, removed
   debugpushkey: 
   debugpvec: 
diff --git a/tests/test-obsolete.t b/tests/test-obsolete.t
--- a/tests/test-obsolete.t
+++ b/tests/test-obsolete.t
@@ -129,6 +129,13 @@ Register two markers with a missing node
   ca819180edb99ed25ceafb3e9584ac287e240b00 1337133713371337133713371337133713371337 0 (Thu Jan 01 00:22:18 1970 +0000) {'user': 'test'}
   1337133713371337133713371337133713371337 5601fb93a350734d935195fee37f4054c529ff39 0 (Thu Jan 01 00:22:19 1970 +0000) {'user': 'test'}
 
+Test the --index option of debugobsolete command
+  $ hg debugobsolete --index
+  0 245bde4270cd1072a27757984f9cda8ba26f08ca cdbce2fbb16313928851e97e0d85413f3f7eb77f C (Thu Jan 01 00:00:01 1970 -0002) {'user': 'test'}
+  1 cdbce2fbb16313928851e97e0d85413f3f7eb77f ca819180edb99ed25ceafb3e9584ac287e240b00 0 (Thu Jan 01 00:22:17 1970 +0000) {'user': 'test'}
+  2 ca819180edb99ed25ceafb3e9584ac287e240b00 1337133713371337133713371337133713371337 0 (Thu Jan 01 00:22:18 1970 +0000) {'user': 'test'}
+  3 1337133713371337133713371337133713371337 5601fb93a350734d935195fee37f4054c529ff39 0 (Thu Jan 01 00:22:19 1970 +0000) {'user': 'test'}
+
 Refuse pathological nullid successors
   $ hg debugobsolete -d '9001 0' 1337133713371337133713371337133713371337 0000000000000000000000000000000000000000
   transaction abort!