Five different castles were used for the castle in this film.
Was originally to be directed by Alejandro Jodorowsky and produced by Allen Klein. Klein had funded Jodorowsky's two previous pictures, El Topo (1970) and The Holy Mountain (1973). However, Alejandro bailed on the film leaving Klein with the problem of finding a replacement, which he never did. After much trouble with trying to get it off the ground, Klein sold the rights. However, the ordeal spawned a 30-year feud with Jodorowsky, and resulted in Klein withholding the rights to El Topo and The Holy Mountain, blocking them from being distributed. The feud was finally settled in 2005.
The role of "O" was originally offered to Anulka Dziubinska though she declined on the advice of her agent.
The role of "O" was offered to Brigitte Fossey. She had an interview with Just Jaeckin but declined because of strong nudity.