Indoors only. Twice, Belle escaped out the back door when someone didn't close it, but she just sat on the back porch and waited to be let back in. Dum dum (Roscoe) knocked out a hole in the fence in the backyard big enough that they could escape through it, or I may let them in the backyard occasionally....although I seriously doubt it. I'd just worry too much, and they are perfectly happy indoors.