diff --git a/oauth2client/appengine.py b/oauth2client/appengine.py
index e4169e9..f97ce69 100644
--- a/oauth2client/appengine.py
+++ b/oauth2client/appengine.py
@@ -263,6 +263,16 @@
     if self._cache:
       self._cache.set(self._key_name, credentials.to_json())
 
+  def locked_delete(self):
+    """Delete Credential from datastore."""
+
+    if self._cache:
+      self._cache.delete(self._key_name)
+
+    entity = self._model.get_by_key_name(self._key_name)
+    if entity is not None:
+      entity.delete()
+
 
 class CredentialsModel(db.Model):
   """Storage for OAuth 2.0 Credentials
diff --git a/oauth2client/client.py b/oauth2client/client.py
index 2d60f5a..f492563 100644
--- a/oauth2client/client.py
+++ b/oauth2client/client.py
@@ -224,6 +224,13 @@
     """
     _abstract()
 
+  def locked_delete(self):
+    """Delete a credential.
+
+    The Storage lock must be held when this is called.
+    """
+    _abstract()
+
   def get(self):
     """Retrieve credential.
 
@@ -252,6 +259,21 @@
     finally:
       self.release_lock()
 
+  def delete(self):
+    """Delete credential.
+
+    Frees any resources associated with storing the credential.
+    The Storage lock must *not* be held when this is called.
+
+    Returns:
+      None
+    """
+    self.acquire_lock()
+    try:
+      return self.locked_delete()
+    finally:
+      self.release_lock()
+
 
 class OAuth2Credentials(Credentials):
   """Credentials object for OAuth 2.0.
diff --git a/oauth2client/file.py b/oauth2client/file.py
index d71e888..1abc6d2 100644
--- a/oauth2client/file.py
+++ b/oauth2client/file.py
@@ -85,7 +85,6 @@
       finally:
         os.umask(old_umask)
 
-
   def locked_put(self, credentials):
     """Write Credentials to file.
 
@@ -97,3 +96,12 @@
     f = open(self._filename, 'wb')
     f.write(credentials.to_json())
     f.close()
+
+  def locked_delete(self):
+    """Delete Credentials file.
+
+    Args:
+      credentials: Credentials, the credentials to store.
+    """
+
+    os.unlink(self._filename)
diff --git a/oauth2client/multistore_file.py b/oauth2client/multistore_file.py
index d9b89c8..1f756c7 100644
--- a/oauth2client/multistore_file.py
+++ b/oauth2client/multistore_file.py
@@ -159,6 +159,17 @@
       """
       self._multistore._update_credential(credentials, self._scope)
 
+    def locked_delete(self):
+      """Delete a credential.
+
+      The Storage lock must be held when this is called.
+
+      Args:
+        credentials: Credentials, the credentials to store.
+      """
+      self._multistore._delete_credential(self._client_id, self._user_agent,
+          self._scope)
+
   def _create_file_if_needed(self):
     """Create an empty file if necessary.
 
@@ -344,6 +355,23 @@
     self._data[key] = cred
     self._write()
 
+  def _delete_credential(self, client_id, user_agent, scope):
+    """Delete a credential and write the multistore.
+
+    This must be called when the multistore is locked.
+
+    Args:
+      client_id: The client_id for the credential
+      user_agent: The user agent for the credential
+      scope: The scope(s) that this credential covers
+    """
+    key = (client_id, user_agent, scope)
+    try:
+      del self._data[key]
+    except KeyError:
+      pass
+    self._write()
+
   def _get_storage(self, client_id, user_agent, scope):
     """Get a Storage object to get/set a credential.
 
diff --git a/tests/test_oauth2client_appengine.py b/tests/test_oauth2client_appengine.py
index f2f470f..90ee335 100644
--- a/tests/test_oauth2client_appengine.py
+++ b/tests/test_oauth2client_appengine.py
@@ -203,6 +203,30 @@
     q = parse_qs(response.headers['Location'].split('?', 1)[1])
     self.assertEqual('http://localhost/oauth2callback', q['redirect_uri'][0])
 
+  def test_storage_delete(self):
+    # An initial request to an oauth_required decorated path should be a
+    # redirect to start the OAuth dance.
+    response = self.app.get('/foo_path')
+    self.assertTrue(response.status.startswith('302'))
+
+    # Now simulate the callback to /oauth2callback.
+    response = self.app.get('/oauth2callback', {
+        'code': 'foo_access_code',
+        'state': 'foo_path',
+        })
+    self.assertEqual('http://localhost/foo_path', response.headers['Location'])
+    self.assertEqual(None, self.decorator.credentials)
+
+    # Now requesting the decorated path should work.
+    response = self.app.get('/foo_path')
+
+    # Invalidate the stored Credentials.
+    self.decorator.credentials.store.delete()
+
+    # Invalid Credentials should start the OAuth dance again.
+    response = self.app.get('/foo_path')
+    self.assertTrue(response.status.startswith('302'))
+
   def test_aware(self):
     # An initial request to an oauth_aware decorated path should not redirect.
     response = self.app.get('/bar_path')
diff --git a/tests/test_oauth2client_file.py b/tests/test_oauth2client_file.py
index 7ff1eeb..596a4b6 100644
--- a/tests/test_oauth2client_file.py
+++ b/tests/test_oauth2client_file.py
@@ -98,7 +98,6 @@
     self.assertEquals(data['_module'], OAuth2Credentials.__module__)
 
   def test_token_refresh(self):
-    # Write a file with a pickled OAuth2Credentials.
     access_token = 'foo'
     client_id = 'some_client_id'
     client_secret = 'cOuDdkfjxxnv+'
@@ -122,6 +121,27 @@
     credentials._refresh(lambda x: x)
     self.assertEquals(credentials.access_token, 'bar')
 
+  def test_credentials_delete(self):
+    access_token = 'foo'
+    client_id = 'some_client_id'
+    client_secret = 'cOuDdkfjxxnv+'
+    refresh_token = '1/0/a.df219fjls0'
+    token_expiry = datetime.datetime.utcnow()
+    token_uri = 'https://www.google.com/accounts/o8/oauth2/token'
+    user_agent = 'refresh_checker/1.0'
+
+    credentials = OAuth2Credentials(
+        access_token, client_id, client_secret,
+        refresh_token, token_expiry, token_uri,
+        user_agent)
+
+    s = Storage(FILENAME)
+    s.put(credentials)
+    credentials = s.get()
+    self.assertNotEquals(None, credentials)
+    s.delete()
+    credentials = s.get()
+    self.assertEquals(None, credentials)
 
   def test_access_token_credentials(self):
     access_token = 'foo'
@@ -205,6 +225,11 @@
     self.assertNotEquals(None, credentials)
     self.assertEquals('foo', credentials.access_token)
 
+    store.delete()
+    credentials = store.get()
+
+    self.assertEquals(None, credentials)
+
     if os.name == 'posix':
       self.assertEquals('0600', oct(stat.S_IMODE(os.stat(FILENAME).st_mode)))