The heirs of Donatien Alphonse François de Sade pressed charges to prevent any use of his name on the advertising material. The changes on posters and lobby cards were made at the last minute by sticking the new title "Le Crâne Maléfique" (meaning "The Evil Skull") on top of the former, "Les forfaits du Marquis de Sade" (meaning "the Infamies of Marquis de Sade"). Only on that condition could the movie be released in the French territories.
According to director Freddie Francis, the "screenplay" by producer Milton Subtosky was little more than an outline and a great deal had to be added during filming, and later in post-production, to bring it up to adequate feature length.
The film's account of the life of the Marquis De Sade is fairly preposterous. Although rightly notorious for debauchery and for the particular sexual excesses that led to the word "sadism" being formed from his name, he was never associated with diabolism and had no belief in either the devil or God. Nor was he ever thought to have killed anyone, directly or indirectly. He was the only officer of the French Revolution never to have signed a death warrant. His participation in the Revolution - despite his aristocratic status - came about because of his detestation of the hypocrisy governing Bourbon France, when wealth and ancestry prevented criminal prosecution for crimes and depravities visited upon the poor. His long incarceration in an asylum was occasioned, not by madness, but by the spitefulness of his wife's family (whom he had saved from the guillotine) and by a perceived need to keep him quiet and to prevent his analysis of a corrupt social order being widely disseminated. However, it is said to be true that, shortly after his death in 1814, his grave was vandalized and his skull purloined - a mystery never solved.
Although passed by the BBFC in October 1965, this movie did not get a release in the U.K. until November 1966, when it went out as the bottom half of a double bill with "The Idol" (1966).
Though this was the 12th film Christopher Lee and Peter Cushing starred in, it was the first film in which they played genuine friends with a long history together.