I also have a female cat, Angel, she's estimated to be about 1 and a half (I got her from the humane society). I got another kitten about 2 weeks ago. I got a male, CJ. As of right now I can't say that it was the best choice, but I guess it takes about a month for cats to adjust living together. Angel watches CJ's every move and attempts to play with him every once in a while. She's slowly, very slowly, getting used to having another cat in the house. Anyway, I also think it depends on the individual cat. About 6 years ago I had a male cat and then got a female when the male was probably 5 and they never got along. I know for a fact though that Angel would NOT get along with another female because of her attitude (female cats are more independent). So it really depends on what your cat's attitude is.