When submitted for re-classification in the UK (after being banned for 18 years), the uncut version of this film was never brought before the BBFC (British Board of Film Classification). Rather, the heavily cut, R-rated version was submitted, possibly by mistake.
According to Joe D'Amato, some of the heads and bones in the catacombs were plastic imitations. Upon collecting the bones after the scenes had been shot, the crew by accident took with them some real bones. Since D'Amato did not dare to return them, he let them make a "pilgrimage" to his house.
Luigi Montefiori (aka George Eastman) who co-wrote, co-produce and as well as portrayed the villain of disfigured cannibalistic serial killer Nikos Karamanlis in the film, stated when he went to the premier to see it at the old Cinema Metropolitan in Rome with the producer, only a few people were in the theater watching the movie, then people started to leave and one couple were still inside the same theater with Luigi Montefiori and the producer. Soon when the scene of the pregnant woman was being strangled by the killer and eventually rips her fetus out to eat it, the couple got up and walked out offended due to the horrific scene (even though it was a skinned rabbit but it was something new and disturbing for the time by 1980). Only Montefiori and the producer we're the only ones left inside watching the rest of the film.