diff --git a/python/vcf_b36_to_hg18.py b/python/vcf_b36_to_hg18.py
index 685f826c4..53ae40c2c 100755
--- a/python/vcf_b36_to_hg18.py
+++ b/python/vcf_b36_to_hg18.py
@@ -17,6 +17,7 @@ def main():
     parser.add_option("", "--dry", dest="dry",
                         action='store_true', default=False,
                         help="If provided, nothing actually gets run, just a dry run")
+    parser.add_option("-r","--reverse",dest="reverse",action="store_true",default=False,help="If set, will convert the hg18VCF to a b36VCF (thus reversing the functionality)")
                        
     (OPTIONS, args) = parser.parse_args()
     if len(args) != 2:
@@ -26,22 +27,38 @@ def main():
 
     temp = open("tmp", 'w')
     mitotemp = open("mtmp",'w')
-    for line in open(b36vcf):
-        length = len(line)
-        if length > 2 :
-            if line[0:2] == 'MT' or line[0] == "#":
-                if line[0] == "#":
-                    mitotemp.write(line)
+    if not OPTIONS.reverse:
+        for line in open(b36vcf):
+            length = len(line)
+            if length > 2 :
+                if line[0:2] == 'MT' or line[0] == "#":
+                    if line[0] == "#":
+                        mitotemp.write(line)
+                    else:
+                        spline = line.split("\t")
+                        spline[0] = "chrM"
+                        mitotemp.write("\t".join(spline))
                 else:
-                    spline = line.split("\t")
-                    spline[0] = "chrM"
-                    mitotemp.write("\t".join(spline))
-            else:
-                line = 'chr' + line
+                    line = 'chr' + line
+                    temp.write(line)
+        temp.close()
+        mitotemp.close()
+        os.system("cat mtmp tmp > "+hg18vcf+" ; rm mtmp ; rm tmp")
+    else:
+        for line in open(hg18vcf):
+            if line.startswith("#") :
                 temp.write(line)
-    temp.close()
-    mitotemp.close()
-    os.system("cat mtmp tmp > "+hg18vcf+" ; rm mtmp ; rm tmp")
+            else:
+                spline = line.split("\t")
+                if ( spline[0] == "chrM" ):
+                    spline[0] = "MT"
+                    mitotemp.write("\t".join(spline))
+                else:
+                    spline[0] = spline[0].split("chr")[1]
+                    temp.write("\t".join(spline))
+        temp.close()
+        mitotemp.close()
+        os.system("cat tmp mtmp > "+b36vcf+" ; rm mtmp ; rm tmp")
 
 if __name__ == "__main__":
     main()