I started walking my cats outside at the beginning of summer, so I knew I had to have some flea protection. I hadn't had them on any flea prevention for at least 3 years because they were strictly indoors. Prior to that they would go outside on their own and I used frontline. Frontline seemed to stop working after awhile. I switched to revolution, but that is extremely expensive, especially when you have 3 cats. My only reservation about using this product is that it doesn't kill ticks, just fleas. Even so, I thought I'd give it a try because I figured that I would be able to feel a tick on them as they are always climbing all over me and I'm constantly rubbing them. So far, so good. No fleas or ticks and it doesn't stink nearly as much as frontline.