In the scene where Regan's mother is supernaturally blasted away from the bedside, she is being yanked by the crew by a length of rope. After dozens of takes director William Friedkin was still unhappy with the look of the shot and ordered the crew to haul her more fiercely. The scream in the shot that made the cut was of genuine pain and required no dubbing for effect.

The green vomit that Linda Blair vomited was actually green pea soup.

According to writer William Peter Blatty, the shooting of the film was supposed to about 90 days long. It ended up being shot in about 210 days. He states that 'strange and sinister things happened from the very beginning.'

In the disturbing scene where The Devil/Regan is masturbating with the crucifix Linda Blair said she had no idea what it was supposed to mean, she was just bringing down the crucifix into a box.

Author and writer of the book and script William Peter Blatty has a cameo early in this film. He plays the producer trying to have a word with director Burke Dennings on the movie set before Burke turns his attention to Chris MacNeil. William Peter Blatty is the middle eastern-looking guy with the black hair and moustache, which is natural since his mother is originally from Lebanon.

The Prospect Avenue apartment where the story takes place was once inhabited by the author, William Peter Blatty, while he was a student at Georgetown University. The house is at the corner of 36th and Prospect. Submitted by wizard_of_gore

Was the highest-grossing R-rated film for about ten years until it was unseated by "Beverly Hills Cop" on March 1984.

The nurse who comes into Dr. Taney's office after the arteriogram is actress Linda Blair's mother. Submitted by wizard_of_gore

The scream of the demon being thrown out of Linda Blair was actually created by recording squealing pigs being driven into slaughter.