Once a month and a 10th of a cc for every 10 pounds of dog and I have never had one problem with worms, fleas, ticks or anything else that lives on blood. I caught my vet giving it to his dogs about 12 years ago and he reluctantly gave up the secret. Only warning I got was that it would kill any of the Collie breeds.(Don't ask why cause I don't know) I can't imagine having to buy all of those different products for individual ailments. By the way, anyone reading this will try at his own risk.