I have 2 cats, both 1 year old. When I brought Reese home he wanted to chase them and put them in his mouth. He never bit down, just covered them with drool. The vet said, and I have to agree, if he wanted to hurt them they would be dead. He wants to play and they just don't like his idea of play. The vet and some members here told me to put Reese on his leash and let him go after them when they walked by. Pop the leash and tell him no. Do it over and over until he got the message. Well, he never got the message. He has a very high prey drive and will chase anything small and fast. I now have baby gates all over my house. The cats stay upstairs or in my bedroom when the dog is out of his crate. A lot of members here have cats and Dobes that get along. It can be done, just apparently not at my house. Good luck and let me know if you figure out a solution that works for you.