I just got a puppy 3 weeks ago and have always only had cats. My youngest cat is almost 2 and very playful but my older cat is 10. I was unsure how my baby would take the new pup bc she hated a stray cat we took in over the summer. Needless to say they love eachother...Misty (the baby) follows Jade (the pup) around the house and usually pounces on her once inawhile but she seems to be pretty gentle with her and jade goes after her also...my oldest (shadow) doesnt really like her and still hisses or meows when shes around, but the dog is fine and the cats will adjust, no real need for the dog to have to stay outside all the time, but i agree that getting a puppy would be better or find a dog that was raised with cats...most shelters have those too. Good luck.