I don't think it does as the steam cleaner can't get into all the nooks and crannies, apparently lots live next to the slirting boards and stuff. Sprays are good, but for the carpets i use powder. You sprinkle it over the carpet, leave the room for 30 minutes and then hoover it up. It should kill all the fleas present in the carpet. Bedding will need to be sprayed too. Have the cats been treated? Have you just got the kittens or do you have older cats? Older cats can be treated with frontline spot on or spray, they kill all the fleas that jump onto your pet within 24 hours. (Spot on can be used from 12 weeks and spray can be used from 2 days old, so perfect for the kittens.) You can get both from the vets. (You probably already know this anyway but just incase!) Good luck!