i use frontline, and that works like a charm for me. my fiance and i, and the cat were all getting bitten, thanks to our neighbor's dog. :x you get one flea ridden animal in one apartment in the building and that's all it takes. it took about a month to completely get rid of the fleas once i started using the frontline on the kitty, but there was a definite decrease early on. it takes a while because the fleas have to jump onto the cat to get the frontline on them before they die. but it works really well.