diff --git a/CHANGES.txt b/CHANGES.txt
index dc5d58f..89e961a 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -12,6 +12,8 @@ Next release
 
 - Allow ``quant`` and ``rounding`` args to ``colander.Decimal`` constructor.
 
+- ``luhnok`` validator added (credit card luhn mod10 validator).
+
 0.9.8 (2012-04-27)
 ------------------
 
diff --git a/colander/__init__.py b/colander/__init__.py
index 904c6bd..d40cb6e 100644
--- a/colander/__init__.py
+++ b/colander/__init__.py
@@ -355,6 +355,28 @@ class OneOf(object):
                     mapping={'val':value, 'choices':choices})
             raise Invalid(node, err)
 
+def luhnok(node, value):
+    """ Validator which checks to make sure that the value passes a luhn
+    mod-10 checksum (credit cards).  ``value`` must be a string, not an
+    integer."""
+    sum = 0
+    num_digits = len(value)
+    oddeven = num_digits & 1
+
+    for count in range(0, num_digits):
+        digit = int(value[count])
+
+        if not (( count & 1 ) ^ oddeven ):
+            digit = digit * 2
+        if digit > 9:
+            digit = digit - 9
+
+        sum = sum + digit
+
+    if not (sum % 10) == 0:
+        raise Invalid(node, 
+                      '%r is not a valid credit card number' % value)
+
 class SchemaType(object):
     """ Base class for all schema types """
     def flatten(self, node, appstruct, prefix='', listitem=False):
diff --git a/colander/tests/test_colander.py b/colander/tests/test_colander.py
index 72b8b9f..8afb1e9 100644
--- a/colander/tests/test_colander.py
+++ b/colander/tests/test_colander.py
@@ -408,6 +408,25 @@ class TestOneOf(unittest.TestCase):
         e = invalid_exc(validator, None, None)
         self.assertEqual(e.msg.interpolate(), '"None" is not one of 1, 2')
 
+class Test_luhnok(unittest.TestCase):
+    def _callFUT(self, node, value):
+        from colander import luhnok
+        return luhnok(node, value)
+
+    def test_fail(self):
+        import colander
+        val = '10'
+        self.assertRaises(colander.Invalid, self._callFUT, None, val)
+
+    def test_fail2(self):
+        import colander
+        val = '99999999999999999999999'
+        self.assertRaises(colander.Invalid, self._callFUT, None, val)
+
+    def test_success(self):
+        val = '4111111111111111'
+        self.assertFalse(self._callFUT(None, val))
+
 class TestSchemaType(unittest.TestCase):
     def _makeOne(self, *arg, **kw):
         from colander import SchemaType
diff --git a/docs/api.rst b/docs/api.rst
index e92ec02..c05dea3 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -65,6 +65,8 @@ Validators
 
   .. autoclass:: Email
 
+  .. autofunction:: luhnok
+
 Types
 ~~~~~