Frontline doesn't prevent the ticks from getting on the animal, but once it attaches itself, it will die. That's better than having them living on our pets, I guess. Just the other day, I saw my Lilly messing with something on the floor, and it was a dead, fat tick. But at least it was dead! We have already seen quite a few ticks this year, and all of my cats and dogs are treated with Frontline Plus monthly. But, we do have to watch ourselves too, because SAS is right and we can bring them inside just as easily as the animals can.