If you own two cats that are behaving aggressively toward each other, try disciplining them by separating the cats. For some, placing the aggressor in another room in "time out" for an hour or two will stop the problem. While the instigator is in a separate room, make sure the other cat can move about freely throughout the rest of the house. In some instances, an hour or two of separation is not enough. If the aggression continues, you may have to separate the cats for a longer period of time. Some people report good results after a few days, while a few have reported that it can take several weeks or even months for the cats to grow out of their aggressive cat behavior. Since aggressive cat behavior is one of the biggest reasons cat owners get rid of their cats, it makes sense to stop this behavior early by separating your aggressive cats.