We've been using Pine Wood pellets as cat litter for several years now. No problems at all. All 5 cats are happy and healthy (and so is our bank account). We had been using cheapo clay litter before that. To help the kitties get used to the change, we started out with mostly clay litter with just a little bit of the pine pellets. We gradually added more and more pine pellets but still mix in clay since the cats like it.