From The Grindhouse Cinema Database
- The second part (with Suspiria (1977) and Terza madre, La (2007)) of the "Three Mothers" trilogy.
- James Woods was the original choice for the lead role but he was already committed to Videodrome (1983).
- All of the murderer's hands in the movie were Dario Argento's.
- Legendary Italian horror director Mario Bava assisted with the making of the special effects on this film. Bava passed away shortly before its release.
- For some of the exterior location shoots in Italy footage of New York City skyscrapers were superimposed in the background to make it appear like the films NYC setting.
- In an interview with assistant director Lamberto Bava, he said that he handled and wrangled so many cats during the shooting of this film that afterward he could no longer stand to be in the same room as a cat. He's avoided them since then.
- Argento said that the gentleman who provided the live ants used in the film collected them by walking around in the park with a vacuum and literally sucking them up from the ground. He would later retrieve them from the vacuum bag once on set.
- Part of the reason Argento cast Irene Miracle as Rose Elliot was she had synchronize swimming skills, which came in quite handy for the shooting of the underwater ballroom scene.