diff --git a/api-ref/source/os-security-group-rules.inc b/api-ref/source/os-security-group-rules.inc
index 896fb68cfbf3..ab6c958535a5 100644
--- a/api-ref/source/os-security-group-rules.inc
+++ b/api-ref/source/os-security-group-rules.inc
@@ -16,6 +16,10 @@ Create Security Group Rule
 Creates a rule for a security group. Either ``cidr`` or ``group_id`` must be
 specified when creating a rule.
 
+.. note::
+    nova-network only supports ingress rules. If you want to define egress
+    rules you must use the Neutron networking service.
+
 Normal response codes: 200
 
 Error response codes: badRequest(400), unauthorized(401), forbidden(403)