the other option, although more expensive, is to get a flea jab from your vets. It costs about �30 for 6 months, but if you think of �5 a month it's not so bad! My cats have always been an absolute nightmare with any spot-on treatments and if your not careful they get all over the shop, and not just your cat! I find the jab to be the best way of ensuring the job gets done. Definately need to massivley de-flea the house as well though - 95% of the fleas will NOT be on your cats, but in your house!!!