What is the best way to introduce a new cat into a multi-cat household?

The first thing we suggest about bringing another cat into your house is that you have it feline leukemia tested before introducing him to your existing cat(s). When you are sure your new cat has tested negative for feline leukemia, shut him in an extra room along with his litter, food and water for at least a week or two. (This room will become a "safe spot" for your new cat. Anytime he gets spooked in the future, he'll return to this room for comfort). While your new cat is getting adjusted to his new surroundings, it allows your existing cat to smell his new friend under the door. After about 3-4 days, open the door and let your cats see each other, but don't let them get close. Use a screen or baby gate so they can view each other safely. In another day or two, open the door again and let them get closer. Continue this process… It is very important that you give both cats equal attention throughout the process. Some cats will adjust very quickly and get along fine while others will take much longer. Some cats will never become buddies; they will only tolerate each other's existence.