Co-writer Bernardino Zapponi said the inspiration behind the murder scenes came from him and Dario Argento thinking of painful injuries that the audience could relate to. Basically, not everyone knows the pain of being shot by a gun, but everyone has at some point accidentally struck furniture or been scalded by hot water.
The close-up shots of the killer's hands, clad in black leather gloves, were performed by director Dario Argento himself.
In one scene David Hemmings walks past the Blue Bar at night. The bar is styled after the famous painting "Nighthawks", by Edward Hopper.
The role of Carlo's male transvestite lover, Massimo Ricci, was actually played by actress Geraldine Hooper.
After the international success of Dario Argento's next film Suspiria (1977), "Profondo Rosso" was released in Japan under the title "Suspiria 2", even though it has no plot connections to "Suspiria" and was made two years prior to it.