- Ellen Burstyn agreed to doing the movie only if her character didn't have to say the scripted line: "I believe in the devil!" The producers agreed to eliminate the utterance.
- John Boorman had been offered the chance to direct "The Exorcist" but declined because he felt the storyline was "cruel towards children". He did, however, accept the offer to direct Exorcist II: The Heretic (1977).
- Dana Plato was offered the role of Regan MacNeil.
- Anissa Jones was tested for the role of Regan MacNeil.
- Mercedes McCambridge had to sue Warner Brothers for credit as the voice of the demon.
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