The basis of the movie is a woman who has hemophilia. Although this is generally a condition which affects men, there are documented cases of female hemophiliacs.
The 'mutilated' bodies in Pratt's apartment are real bodies, transformed into art by the German sculptor Gunther von Hagens.
feardotcom.com is/was the address of the movie's official Web site.
Polidori, the doctor played by Udo Kier, shares his name with the surgeon to Lord Byron who was present on the night that Mary Shelley came up with the idea for "Frankenstein". Dr. Polidori was also a character in "Frankenstein the True Story" - 1973... also starring Michael Sarrazin. Sarrazin refers to the Polidori character in both films as "Polly Dolly", and in both films Polidori was killed by electricity.
The glass cases containing body parts from House on Haunted Hill (1999) make an appearance.
The name "Dr. Gogol" is written on the subway wall in the first scene. This is a reference to Mad Love (1935), another film about a mad surgeon.
Some of the sets were leftovers from the 2001 action film "The Musketeer", also made by the same studio.
In pre-production the website featured in the film was called Fear.com, despite the producers not owning that website in real-life. They had hoped to buy the domain name from its owners at the time, but were told that it was not for sale at any price, leading to the website's name in the film being changed to Feardotcom.com.
Several of the film's subterranean sets were re-used from the 2001 action pic "The Musketeer" - also made by the same production company.
Although Franchise Pictures is listed as a production company, the studio only came on board the film late in post-production and used their deal with Warner Bros. to get the film a stateside theatrical release.