Michael Crichton was invited to take a tour of Universal Studios during the production of this film. His guide was none other than Steven Spielberg, who went on to adapt Crichton's most successful novel, Jurassic Park (1993).
Michael Crichton wrote the rough draft for the novel from which this film is adapted while he was still a medical student. He was inspired after a conversation with one of his teachers about the concept of crystal-based life-forms.
When Dr. Stone's wife tells him someone is at the door to see him, he says, "The SDS has arrived, no doubt." "SDS" is an acronym for "Students for a Democratic Society", a protest group active in colleges in the late 1960s.
The computer error "601" occurs because of a system overload while trying simulate Andromeda's growth and mutation. The error number is a reference to the computer overload error of "1202" (exactly double) which occurred on the LEM during the first lunar descent.
Leavitt, in a protest against inserting something to clean out the GI tract, makes the statement about "risked drowning in that foul bath". The book, but not the movie, had the Wildfire Team submerge completely in an antibiotic solution. The scene may have been cut, but Leavitt still makes reference to it in the movie.
Screenwriter Nelson Gidding broached the idea to director Robert Wise that one of the four scientists should be a woman. Wise initially envisioned female character being something like Raquel Welch in Fantastic Voyage (1966) and objected strenuously to the change. However, after Gidding described in detail the character eventually played by Kate Reid, he convinced Wise that it was a positive addition to the story.
At the plane crash site, the actor who was supposed to call out, "Major Mancheck," fell out of his trailer and broke his leg. He was replaced on the spot with Robert 'Bob' Olen, who did the lines but was never credited for it.
The section of the film where the two scientists are in the town of Piedmont in their suits, is very similar to the opening of The Man from U.N.C.L.E.: The Finny Foot Affair (1964). They were even searching for some kind of biohazard material, too, which had been taken to a local doctor, but in a small town in Scotland, where they also found everyone dead. In the "UNCLE" episode, the biohazard caused rapid aging, which resulted in death.
Mapping data shown for location of WildFire was from a Aeronautical Sectional Chart. The location of WildFire, as depicted, is just North of Searchlight NV and East of I-95 at approximately N35:31.94 W114:52.80. The statement regarding the reason for selection of the site was that there was no inhabitable area for a radius of 112 miles was erroneous since Las Vegas is only 27nm miles north.
The trivia item below may give away important plot points.
The monkey was "killed" by being placed in a large set filled with carbon dioxide. When the monkey's cage, which contained oxygen, was opened the animal was rendered unconscious by the CO2. An assistant director was off camera and brought a breathing apparatus to the monkey, who recovered immediately.