diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index 11c7a5ed9a..3452736162 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -1056,25 +1056,6 @@ class ManyToManyField(RelatedField, Field):
                     break
         return getattr(self, cache_attr)
 
-    def isValidIDList(self, field_data, all_data):
-        "Validates that the value is a valid list of foreign keys"
-        mod = self.rel.to
-        try:
-            pks = map(int, field_data.split(','))
-        except ValueError:
-            # the CommaSeparatedIntegerField validator will catch this error
-            return
-        objects = mod._default_manager.in_bulk(pks)
-        if len(objects) != len(pks):
-            badkeys = [k for k in pks if k not in objects]
-            raise exceptions.ValidationError(
-                ungettext("Please enter valid %(self)s IDs. The value %(value)r is invalid.",
-                          "Please enter valid %(self)s IDs. The values %(value)r are invalid.",
-                          len(badkeys)) % {
-                'self': self.verbose_name,
-                'value': len(badkeys) == 1 and badkeys[0] or tuple(badkeys),
-            })
-
     def value_to_string(self, obj):
         data = ''
         if obj: