My cat and I are moving in with other cats and a dog!

Introduce them slowly. Initially keep them segregated in different rooms. I recommend putting the new cats in a room and letting the cats that lived there roam and get used to their smell through the door before socializing them further.

I also find meal-time introduction can be helpful. If they are put in the same room with separate food and are very hungry, they may not bother checking each other out and focus on the food instead and get used to each other more slowly.

If they just won't get along, there's not much you can do about it but you can try to at least get them off on the right foot by not triggering more territoriality than you need to. Easing the new animals in will be easier on the existing animals and make them feel less threatened.

Thanks Robert! That seems to be the concensus on other sites. The meal-time introduction seems like a good idea, I hadn't heard that before. Your help is much appreciated!

Help! My cat has been in her own room for nearly 3 weeks. I have tried socializing slowly but one of the other cats doesn't seem to understand hissing and they end up in a tussle. How do I ease her in? Evrytime she is out of the room she gets so stressed out and angry that she won't let anyone near her. Any thoughts?

I'm not sure what to tell you, sometimes no matter what you try it doesn't work. I've know a few cats who refuse to get along no matter what I've tried.

They eventually took over different "territory" in the house and got pissy any time they were near each other but learned to ignore each other for the most part.

True. My own experience with introducing a new cat to one or two other cats makes me think that tossing the new cat in, on a sink or swim, work it out yourselves is at least as good as any other method. I recognize you are working with much larger numbers of animals, but I don't think there's much else you can do right now.