I, too, used clumping litter for a number of years with my ferrets, and while I never had problems with respiratory or other physical ailments, I found the litter scattered everywhere and was very hard to clean. It would get into every crook and crevice and I know it won't come out. As far as the physical problems with clumping litter, I believe it expands to 13 times its original size. Now just figure what would happen if your fuzzy snuffed it up his nose or got some stuck to his/her rear! I've found the best litter for my multi-ferret household is the pine pellet litter (one brand name is PineFresh). I know people have had difficulty in getting this sometimes, but PetSmart is now carrying a brand of it (20 lbs. for $8). Amy & Dave (and their gaggle of giggling ferrets) RIP Ian and Elektra [Posted in FML issue 1578]