diff --git a/django/core/validators.py b/django/core/validators.py
index 8ac9a96cc7..46b1e4fc36 100644
--- a/django/core/validators.py
+++ b/django/core/validators.py
@@ -7,7 +7,7 @@ from django.utils.encoding import smart_unicode
 # These values, if given to to_python(), will trigger the self.required check.
 EMPTY_VALUES = (None, '')
 
-def validate_integer(value, all_values={}, model_instance=None):
+def validate_integer(value):
     try:
         int(value)
     except (ValueError, TypeError), e:
@@ -18,6 +18,28 @@ email_re = re.compile(
     r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*"' # quoted-string
     r')@(?:[A-Z0-9]+(?:-*[A-Z0-9]+)*\.)+[A-Z]{2,6}$', re.IGNORECASE)  # domain
 
-def validate_email(value, all_values={}, model_instance=None):
+def validate_email(value):
     if not email_re.search(smart_unicode(value)):
         raise ValidationError(_(u'Enter a valid e-mail address.'))
+
+class ComplexValidator(object):
+    def get_value(self, name, all_values, obj):
+        assert all_values or obj, "Either all_values or obj must be supplied"
+
+        if all_values:
+            return all_values.get(name, None)
+        if obj:
+            return getattr(obj, name, None)
+        
+
+    def __call__(self, value, all_values={}, obj=None):
+        raise NotImplementedError()
+
+class RequiredIfOtherFieldBlank(ComplexValidator):
+    def __init__(self, other_field):
+        self.other_field = other_field
+
+    def __call__(self, value, all_values={}, obj=None):
+        if self.get_value(self.other_field, all_values, obj) in EMPTY_VALUES:
+            if value in EMPTY_VALUES:
+                raise ValidationError('This field is required if %n is blank.' % self.other_field)
diff --git a/django/forms/fields.py b/django/forms/fields.py
index 9446ed2eea..d65edd7047 100644
--- a/django/forms/fields.py
+++ b/django/forms/fields.py
@@ -119,6 +119,11 @@ class Field(object):
     def validate(self, value):
         if value in EMPTY_VALUES and self.required:
             raise ValidationError(self.error_messages['required'])
+        for v in self.validators:
+            # don't run complex validators since they need all_values
+            # and must therefore be run on the form level
+            if not isinstance(v, validators.ComplexValidator):
+                v(value)
 
 
     def clean(self, value):
diff --git a/django/forms/forms.py b/django/forms/forms.py
index b5c0fc06e0..912fd7c031 100644
--- a/django/forms/forms.py
+++ b/django/forms/forms.py
@@ -5,6 +5,7 @@ Form classes
 from copy import deepcopy
 
 from django.core.exceptions import ValidationError
+from django.core.validators import ComplexValidator
 from django.utils.datastructures import SortedDict
 from django.utils.html import conditional_escape
 from django.utils.encoding import StrAndUnicode, smart_unicode, force_unicode
@@ -254,6 +255,9 @@ class BaseForm(StrAndUnicode):
             if not name in self.cleaned_data:
                 continue
             for v in field.validators:
+                # skip noncomplex validators, they have already been run on the Field
+                if not isinstance(v, ComplexValidator):
+                    continue
                 try:
                     v(self.cleaned_data[name], all_values=self.cleaned_data)
                 except ValidationError, e: