In the scene where the two priests are driving to the Lutz house and the car goes out of control, they alternate between shots of Rod Steiger and Don Stroud. The car's windows switch between closed and open in various shots.
When James Brolin was offered the role of George Lutz, he was informed that they didn't have a script to give him. James bought a copy of the novel and began to read it. At two o'clock in the morning, while reading a very intense part of the book, a pair of pants that he had hung up earlier fell to the ground causing him to jump in fright. After that, James agreed to do the film.