My roommates cat is VERY aggressive towards Corkscrew, she makes it clear that she doesn't like Tibby but she isn't as aggresive. I think it's because Tibby is so much younger and smaller that Corkscrew and Sasha (my roommates cat). It's been way over a year and things haven't gotten better. While at first my roommate and I were so scared by it now we've learned to ignore it. If it starts to get too ugly we spray them with the squirt gun.