If this film was released today, it would be rated PG-13 for some violence, language, and brief sexual references.
The end credits scene and the musical score of the credits is extremely creepy. It's not for kids to see. And being this was a few years before PG-13 (and even by PG-13 standards this movie is still pretty much leaning on an R today, or at least was in the early 80s). Everything about the nature of prison is creepy in this movie.
(See above) a man cuts off his fingers with an axe.
Fight scenes may be frightening to some.
As this is a thriller, many parts in this movie are extremely suspenseful and/or intense.