Advantage is the first flea control for my 3 cats that seems to be effective.  We have tried lots of products and this is the bomb.  No more fleas on the cats, no more fleas on my ankles, no more fleas period.  You'll need one dose per cat per month.  I got the six pack and treat all 3 for 2 months at a time.  This stuff is alot more expensive at the pet store.  Found it on Amazon and bought it from a place that resells overstock.  The box was wrinkled, but the contents were in perfect shape.  Paid an excellent price, I think around 34.00 for 6 doses of the up to 9 pound cat mixture, and the shipping was free!  Quit wasting your time with other stuff and simply give it a try.