diff --git a/hgext/convert/common.py b/hgext/convert/common.py
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -5,7 +5,7 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
-import base64, errno, subprocess, os, datetime
+import base64, errno, subprocess, os, datetime, re
 import cPickle as pickle
 from mercurial import util
 from mercurial.i18n import _
@@ -63,6 +63,15 @@ class converter_source(object):
 
         self.encoding = 'utf-8'
 
+    def checkhexformat(self, revstr):
+        """ fails if revstr is not a 40 byte hex. mercurial and git both uses
+            such format for their revision numbering
+        """
+        matchobj = re.match(r'[0-9a-fA-F]{40,40}$', revstr)
+        if matchobj is None:
+            raise util.Abort(_('splicemap entry %s is not a valid revision'
+                               ' identifier') % revstr)
+
     def before(self):
         pass
 
@@ -164,6 +173,13 @@ class converter_source(object):
         """
         return {}
 
+    def checkrevformat(self, revstr):
+        """revstr is a string that describes a revision in the given
+           source control system.  Return true if revstr has correct
+           format.
+        """
+        return True
+
 class converter_sink(object):
     """Conversion sink (target) interface"""
 
diff --git a/hgext/convert/convcmd.py b/hgext/convert/convcmd.py
--- a/hgext/convert/convcmd.py
+++ b/hgext/convert/convcmd.py
@@ -121,9 +121,17 @@ class converter(object):
         self.splicemap = self.parsesplicemap(opts.get('splicemap'))
         self.branchmap = mapfile(ui, opts.get('branchmap'))
 
+    def parsesplicemap(self, path):
+        """ check and validate the splicemap format and
+            return a child/parents dictionary.
+            Format checking has two parts.
+            1. generic format which is same across all source types
+            2. specific format checking which may be different for
+               different source type.  This logic is implemented in
+               checkrevformat function in source files like
+               hg.py, subversion.py etc.
+        """
 
-    def parsesplicemap(self, path):
-        """Parse a splicemap, return a child/parents dictionary."""
         if not path:
             return {}
         m = {}
@@ -136,18 +144,28 @@ class converter(object):
                     continue
                 try:
                     child, parents = line.split(' ', 1)
+                    self.source.checkrevformat(child)
                     parents = parents.replace(',', ' ').split()
+                    # check if number of parents are upto 2 max
+                    if (len(parents) > 2):
+                        raise util.Abort(_('syntax error in %s(%d): child '\
+                                            'parent1[,parent2] expected') \
+                                            % (path, i + 1))
+                    for parent in parents:
+                        self.source.checkrevformat(parent)
                 except ValueError:
-                    raise util.Abort(_('syntax error in %s(%d): child parent1'
-                                       '[,parent2] expected') % (path, i + 1))
+                    raise util.Abort(_('syntax error in %s(%d): child '\
+                                        'parent1[,parent2] expected') \
+                                        % (path, i + 1))
                 pp = []
                 for p in parents:
                     if p not in pp:
                         pp.append(p)
                 m[child] = pp
-        except IOError, e:
-            if e.errno != errno.ENOENT:
-                raise
+         # if file does not exist or error reading, exit
+        except IOError:
+            raise util.Abort(_('splicemap file not found or error reading %s:')
+                               % path)
         return m
 
 
diff --git a/hgext/convert/hg.py b/hgext/convert/hg.py
--- a/hgext/convert/hg.py
+++ b/hgext/convert/hg.py
@@ -397,3 +397,7 @@ class mercurial_source(converter_source)
 
     def getbookmarks(self):
         return bookmarks.listbookmarks(self.repo)
+
+    def checkrevformat(self, revstr):
+        """ Mercurial, revision string is a 40 byte hex """
+        self.checkhexformat(revstr)
diff --git a/tests/test-convert-splicemap.t b/tests/test-convert-splicemap.t
--- a/tests/test-convert-splicemap.t
+++ b/tests/test-convert-splicemap.t
@@ -37,6 +37,8 @@
   $ hg ci -Am addaandd
   adding a
   adding d
+  $ INVALIDID1=afd12345af
+  $ INVALIDID2=28173x36ddd1e67bf7098d541130558ef5534a86
   $ CHILDID1=`hg id --debug -i`
   $ echo d >> d
   $ hg ci -Am changed
@@ -53,7 +55,7 @@
   o  0:527cdedf31fb "addaandd" files: a d
   
 
-test invalid splicemap
+test invalid splicemap1
 
   $ cat > splicemap <<EOF
   > $CHILDID2
@@ -62,6 +64,24 @@ test invalid splicemap
   abort: syntax error in splicemap(1): child parent1[,parent2] expected
   [255]
 
+test invalid splicemap2
+
+  $ cat > splicemap <<EOF
+  > $CHILDID2 $PARENTID1, $PARENTID2, $PARENTID2
+  > EOF
+  $ hg convert --splicemap splicemap repo2 repo1
+  abort: syntax error in splicemap(1): child parent1[,parent2] expected
+  [255]
+
+test invalid splicemap3
+
+  $ cat > splicemap <<EOF
+  > $INVALIDID1 $INVALIDID2
+  > EOF
+  $ hg convert --splicemap splicemap repo2 repo1
+  abort: splicemap entry afd12345af is not a valid revision identifier
+  [255]
+
 splice repo2 on repo1
 
   $ cat > splicemap <<EOF