I TOO have had a cat problem.......one of mine, the great big black/white one (who should have been named Fat ALbert) has decided that he likes the carpet behind the couch in the den............as his private litter box......I was in there, thinking it sure did smell yuk and strange, and I started looking for whatever it was......yep, I found it alright.......so far, I have tried several things (like plastic bags, all over that carpet, cats hate that sound) and flea spray (they hate that too) but he still trys to go back there......any suggestions from anyone on this? he is fat and old, but he has never been a thin cat anyways (at least, not once he got rescured and gets plenty of food).