A landmark film in Italian cinema, as Sei donne per l'assassino was the film that began the 'giallo' genre. The giallo genre remains Italy's longest running cinematic movement.
Actress Mary Arden wrote most of the English dialog for the film, as she was the only English-speaking member of the production and the film was being shot in English for overseas marketing.
Due to the film's low budget Mario Bava mounted the camera on a child's wagon and used it for tracking shots.
Filmed in six weeks.
For its original release in America the distributors disliked Bava's opening credits that showed the cast posed around the salon in a series of creative tracking shots. The distributors had new opening credits made that showed a series of macabre animations of mannequins being shot.
More graphic images of Peggy's burning face on the hot stove were cut from the film.
The burn makeup for Mary Arden's face would take four hours to apply. One evening after shooting Arden was too tired to have it removed from her face and went home wearing the grisly makeup. Arden's mother, who was living with her at the time, was very alarmed when she saw her daughter come in.
The German titles for the film were 'Bloody Silk' and 'The Masked Strangler'
The title of the film for its release in Denmark was 'Red Nights of the Iron Hand', referring to the metal weapon used in Nicole's murder.
While shooting the scene where Peggy's body falls out of the car trunk a painful mishap occurred. In one take the trunk lid wasn't opened far enough and the lid slammed back down striking Mary Arden painfully in the face. Bava halted the filming and quickly saw to Arden's injuries. The mishap would leave a scar on Arden's face.