"Strange, i have used Advantage on my cat Chloe with good results for years. When i adopted my dog Willow, i figured Advantage would work on her also. It doesnt, not at all! Within one week, she was itching and scratching, and i saw a flea on her. I tried another application, same bad results, even though it had been only 2 weeks since the first dose. Still fleas. I returned to Petco and got Frontline Plus which worked amazing and lasts 4-6 weeks on my dog. I cannot recommend Advantage for dogs. In reading these reviews, maybe its just my dog, but Advantage didnt work for us. Although i would give Advatage 5 stars for my Cat."