During pre-production, the actors worked with medical technical advisor Ruth F. Ekholm, who tutored them on the proper medical procedures for the scenes in which the students flatline on the EKG and EEG machines, signaling cardiac and brain death, respectively. They also took advantage of Peter Filardi's research of published accounts from people who'd had near-death experiences. Almost all accident victims reported a tunnel leading to a beautiful white light and friendly voices. People who had attempted suicide had troubled, emotionally painful near-death experiences.
Julia Roberts (Dr. Rachel Mannus) and Kiefer Sutherland (Nelson Wright) started dating during filming. They ended up engaged, but Roberts ultimately broke it off. She later married Lyle Lovett.
Following a brief period of rehearsals, Joel Schumacher assembled the film's cast and crew in Chicago on October 23, 1989. For two nights, the Museum of Science and Industry was used as the ominous exterior of the Taft Building. For the exterior of the university campus, the production selected the scenic Lake Shore campus of Loyola University.
Julia Roberts said of her Dr. Rachel Mannus character in this film: "All five people in this movie have a different reason for wanting to do this. My character is almost obsessed with the idea of death, and making sure that when you die you're going to a good place." Moreover, Roberts said of the film: "Everybody has experienced loss, and wished they had said something, or done something they didn't get a chance to. This movie is about finding those opportunities".
Kiefer Sutherland described this as "The Breakfast Club Dies" and "St Elmo's Funeral" jokingly in a Fangoria interview.