Established by many reviewers (including director George A. Romero himself) as a graphic blueprint for Night of the Living Dead.
The script was written in part by Richard Matheson, but he was dissatisfied with the result and was therefore credited as Logan Swanson.
This film was originally going to be produced by Hammer Films of Great Britain. They decided not to make it and passed the script over to their U.S. associate, Robert L. Lippert, who produced the film in Italy.