my cat is being extremely aggressive

How long have they been living together? How old is the aggressive one? How many cats all together?

They have been living together since the aggressive one was four weeks old. She is now 11 1/2. The older cat practically raised her from kittenhood. Otherwise, we have three cats. We introduced a 5 month old kitten to the house about a month and a half ago, but this aggressive behavior has been going on for much longer.

Are all the cats female? How do they act toward the kitten? Do you group feed or do they have their own dishes. What specifically does the agressive one do? Names of cats so I will know whom I'm talking about.

Here goes. All of the cats are female. The oldest is Mewie, the aggressive middle child is Bugg and the new kitten is Mollie. Since Mollie came on board, I've been setting out three dishes.

Bugg's aggressiveness started over a year ago, when we moved into an apartment that had another cat living in it (my roommate's cat, Ellie, male, fixed).

Since then, Bugg has been stalking Mewie, pinning her down and clawing and biting her.

I moved again this past August, and Bugg hasn't laid off Mewie since we got here. While there was another cat here before them, I thoroughly cleaned the new apartment to get rid of the smell.

Bugg interacts okay with Mollie, as does Mewie, but Bugg and Mewie are like oil and water.

Well it seems that Bugg has a lot of territorial issues. Since her problem started with the temporary situation with the fourth(male) cat. Bugg is obviously a high strung cat and too old for behavior modification. I suggest that you purchse Feliway (in pet stores). It is a plug in like glade and is a natural tranqilizer which has phenomes and exerts a calming effect on cats. However, if this does not work you will have to speak to your vet about a real tranquilizer for Bugg. It is not fair to Mewie that her last few years on earth are made miserable by Bugg. And Bugg is not happy either. For her own sake she needs to calm down. Mollie has no problems except maybe three's a crowd.