Author Paddy Chayefsky disowned this movie. Even though the dialogue in the screenplay was almost verbatim from his novel he reportedly objected to the over the top shouting of his words by the actors.
In a 1981 interview with the New York Times, Blair Brown said many of the actors and crew tried out the isolation tank. William Hurt actually hallucinated, while Blair Brown found it very peaceful.
At one point, Eddie Jessup mentions the work of "Tart, Ornstein and Deikman." This is a reference to Charles Tart, Robert Ornstein and Arthur Deikman, all of whom wrote books about altered states of consciousness, and all of whom have been involved in modern esoteric spiritual movements, such as the Gurdjieff Work.
One of the few films to be released theatrically with the "Megasound" sound system format. Megasound was a movie theater sound system created by Warner Bros in the early 1980s. It was used to enhance the premiere engagements of a handful of Warner features. Theaters equipped for Megasound had additional speakers mounted on the left, right and rear walls of the auditorium. Selected soundtrack events with lots of low-frequency content (thuds, crashes, explosions, etc) were directed to these speakers at very high volume, creating a visceral effect intended to thrill the audience.