Many, many years ago, we had a *severe* flea problem. My vet recommended a then-new premise spray to be used once in the spring and once in the fall. It was expensive, but I tried it. To this day, I have no flea problem at all - with 5 cats, 3 of them indoor (but go out occasionally) and two semi-ferals who are always out. No fleas - at all - not one - even on the outdoor cats. I attribute this to having sprayed my house, killing the adults fleas, the youngsters, and even the eggs. It's only marginally effective to use spot flea treatment on the cat or dog when the fleas are laying eggs and hatching in the house. Since my vet hospital recommended this particular spray (the original kind from years ago is no longer available), I feel safe in recommending it to my friend.