i definetly would have to say indoors. we live in an apartment complex that is relatively quiet, considering it is a college town, and mostly college students live here, but people still like to zoom through here at break neck speeds. ask my sister's cat, RBJasper....RIP sweet kitty. hit by someone at not even 30, (but its only supposed to be 10mph here) who apparently didnt know they hit him. and he suffered a broken back/neck before he passed. if you live in a neighborhood or somewhere they can roam free, without worries, then please do, i regret not letting my babies be able to roam and eat grass maybe one day i'll move out of the city...