We have six cats and a Standard Poodle. One of the cats is 19, and she doesn't much like anyone except me. The other cats are 13, 4,3, and a pair of not-quite one-year-olds. The babies and the dog play together all the time. There is no fighting or even hissing. We do have to gate off the room where the cats eat and have their litter boxes. That's to keep the dog from eating all the cat food and...well....snacking from the litter boxes, as dogs are wont to do. Otherwise, all is copacetic.