Director Harry Kümel was a passionate admirer of Orson Welles and had him in mind for the role of Cassavius right from the beginning. According to him, it was pretty easy to convince Welles to take the part, once they assured to pay him the salary he asked for. Looking forward to meet and direct his idol, Kümel was pretty nervous when walking onto the set - just to find out that Welles was in a bad mood and drunk. He later stated in interviews that he personally got along well with Welles during the rest of the shoot but the majority of the crew didn't and tried to get out the grumbling Welles' way most of the time.
This film was Harry Kümel's favorite project for a long time but it was not until his previous film Daughters of Darkness (1971) succeeded at the box office (most notably in the US) that he managed to raise funding for it. Unfortunately, "Malpertuis" did poorly in most countries, though it was even nominated for the Palme d'Or at the Cannes Film Festival.