Actor John Kerr was worried about being strapped down to the table with the pendulum above him for the movie's climax. In order to demonstrate that it was perfectly safe, director Roger Corman stood in for Kerr while the scene was being set up.
The film never had an original prologue. It was added when the film was sold to TV and a further few minutes were required to pad out the running time. Only Luana Anders from the original cast was available so an extra scene of her in a madhouse was filmed and tacked on to the beginning. This scene does not really tie in with the rest of the film.
The pendulum was made out of wood and had a rubber blade.
This film was shot in fifteen days.
This was the second of Roger Corman's "Poe" films. He had intended to do "The Masque of the Red Death" but felt that it was too close to the content of Ingmar Bergman's recent Det sjunde inseglet (US title: "The Seventh Seal"). Several years later Corman would go to England to make The Masque of the Red Death.
To increase the pendulum's sense of deadly menace, director Roger Corman took out every other frame during the editing stage making the blade appear to move twice as fast.