diff --git a/moto/ec2/models.py b/moto/ec2/models.py
index 3eaa1a4d..a1165efa 100644
--- a/moto/ec2/models.py
+++ b/moto/ec2/models.py
@@ -373,6 +373,16 @@ class SecurityGroupBackend(object):
             if group:
                 return self.groups[None].pop(group.id)
 
+    def get_security_group_from_id(self, group_id):
+        # 2 levels of chaining necessary since it's a complex structure
+        all_groups = itertools.chain.from_iterable([x.values() for x in self.groups.values()])
+
+        for group in itertools.chain(all_groups):
+            if group.id == group_id:
+                return group
+
+
+
     def get_security_group_from_name(self, name, vpc_id):
         for group_id, group in self.groups[vpc_id].iteritems():
             if group.name == name:
@@ -383,8 +393,14 @@ class SecurityGroupBackend(object):
             default_group = ec2_backend.create_security_group("default", "The default security group", force=True)
             return default_group
 
-    def authorize_security_group_ingress(self, group_name, ip_protocol, from_port, to_port, ip_ranges=None, source_group_names=None, vpc_id=None):
-        group = self.get_security_group_from_name(group_name, vpc_id)
+    def authorize_security_group_ingress(self, group_name, group_id, ip_protocol, from_port, to_port, ip_ranges=None, source_group_names=None, vpc_id=None):
+        # to auth a group in a VPC you need the group_id the name isn't enough
+
+        if group_name:
+            group = self.get_security_group_from_name(group_name, vpc_id)
+        elif group_id:
+            group = self.get_security_group_from_id(group_id)
+        
         source_groups = []
         for source_group_name in source_group_names:
             source_group = self.get_security_group_from_name(source_group_name, vpc_id)
@@ -394,7 +410,7 @@ class SecurityGroupBackend(object):
         security_rule = SecurityRule(ip_protocol, from_port, to_port, ip_ranges, source_groups)
         group.ingress_rules.append(security_rule)
 
-    def revoke_security_group_ingress(self, group_name, ip_protocol, from_port, to_port, ip_ranges=None, source_group_names=None, vpc_id=None):
+    def revoke_security_group_ingress(self, group_name, group_id, ip_protocol, from_port, to_port, ip_ranges=None, source_group_names=None, vpc_id=None):
         group = self.get_security_group_from_name(group_name, vpc_id)
         source_groups = []
         for source_group_name in source_group_names:
diff --git a/moto/ec2/responses/security_groups.py b/moto/ec2/responses/security_groups.py
index 163faa1d..b9223532 100644
--- a/moto/ec2/responses/security_groups.py
+++ b/moto/ec2/responses/security_groups.py
@@ -5,7 +5,15 @@ from moto.ec2.models import ec2_backend
 
 
 def process_rules_from_querystring(querystring):
-    name = querystring.get('GroupName')[0]
+
+    name = None
+    group_id = None
+
+    try:
+        name = querystring.get('GroupName')[0]
+    except:
+        group_id = querystring.get('GroupId')[0]
+
     ip_protocol = querystring.get('IpPermissions.1.IpProtocol')[0]
     from_port = querystring.get('IpPermissions.1.FromPort')[0]
     to_port = querystring.get('IpPermissions.1.ToPort')[0]
@@ -18,7 +26,7 @@ def process_rules_from_querystring(querystring):
     for key, value in querystring.iteritems():
         if 'IpPermissions.1.Groups' in key:
             source_groups.append(value[0])
-    return (name, ip_protocol, from_port, to_port, ip_ranges, source_groups)
+    return (name, group_id, ip_protocol, from_port, to_port, ip_ranges, source_groups)
 
 
 class SecurityGroups(BaseResponse):
diff --git a/tests/test_ec2/test_security_groups.py b/tests/test_ec2/test_security_groups.py
index 24e25f8b..fe330e17 100644
--- a/tests/test_ec2/test_security_groups.py
+++ b/tests/test_ec2/test_security_groups.py
@@ -133,7 +133,7 @@ def test_authorize_other_group_and_revoke():
     security_group.rules.should.have.length_of(0)
 
 @mock_ec2
-def test_authorize_ip_in_vpc():
+def test_authorize_group_in_vpc():
     conn = boto.connect_ec2('the_key', 'the_secret')
     vpc_id = "vpc-12345"
 
@@ -142,5 +142,6 @@ def test_authorize_ip_in_vpc():
     security_group2 = conn.create_security_group('test2', 'test2', vpc_id)
 
     success = security_group1.authorize(ip_protocol="tcp", from_port="22", to_port="2222", src_group=security_group2)
+    success = security_group1.revoke(ip_protocol="tcp", from_port="22", to_port="2222", src_group=security_group2)