diff --git a/django/utils/datastructures.py b/django/utils/datastructures.py
index c1cb6193f5..2779e2ae00 100644
--- a/django/utils/datastructures.py
+++ b/django/utils/datastructures.py
@@ -81,6 +81,9 @@ class MultiValueDict:
     def __len__(self):
         return len(self.data)
 
+    def __contains__(self, key):
+        return self.data.has_key(key)
+
     def get(self, key, default):
         "Returns the default value if the requested data doesn't exist"
         try:
diff --git a/docs/request_response.txt b/docs/request_response.txt
index 85a5e091db..e0b7a01805 100644
--- a/docs/request_response.txt
+++ b/docs/request_response.txt
@@ -31,11 +31,11 @@ All attributes except ``session`` should be considered read-only.
 
 ``GET``
     A dictionary-like object containing all given HTTP GET parameters. See the
-    ``MultiValueDict`` documentation below.
+    ``QueryDict`` documentation below.
 
 ``POST``
     A dictionary-like object containing all given HTTP POST parameters. See the
-    ``MultiValueDict`` documentation below.
+    ``QueryDict`` documentation below.
 
 ``REQUEST``
     For convenience, a dictionary-like object that searches ``POST`` first,
@@ -150,6 +150,10 @@ directly.
     * ``__setitem__(key, value)`` -- Sets the given key to ``[value]``
       (a Python list whose single element is ``value``).
 
+    * ``__contains__(key)`` -- **New in Django development version.*** Returns
+      ``True`` if the given key exists. This lets you do, e.g.,
+      ``if "foo" in request.GET``.
+
     * ``__len__()``
 
     * ``get(key, default)`` -- Uses the same logic as ``__getitem__()`` above,