I also use Revolution for my dog. This is a once a month treatment for flea, tick, mites, and also heartworm prevention and I think it's great. I purchase a one year supply from my vet for about $160.00. It's a bit pricey, but Revolution has strong guarantees if your animal is ever infected with heartworm while using their product. Supposedly, they'll take care of all your pet's medical expenses for heartworm treatment which I hear is extremely expensive. The catch is...you need to have documented evidence that their product was purchased through your vet. I guess the guarantee is void if purchasing through various websites or the 1-800 thing because supposedly some of those places have a history of selling expired or tainted products. I don't know how true all of this is, but I do know that you need to purchase from your vet for them to back you up. All in all it's really pricey preventative treatment, but I guess keeping our furry loved ones healthy is worth it.