The success of the book pretty much guaranteed there would be a film, and a film there was. It was released in 1978 and was a Michael Crichton project from start to finish - novel, screenplay, and direction. Susan Wheeler (Bujold) is a doctor at the prestigious Boston Memorial Hospital. When a good friend (Lois Chiles) comes in for a routine procedure and ends up in a coma she's devastated and wants to know why. As she starts looking into it she finds that a lot of operations on young, healthy people end up with the patient in a coma. Is this just coincidence or is there something more sinister a foot? Her investigations lead her into the dark heart of a conspiracy and very real danger, but even her Doctor boyfriend (Douglas) has trouble believing her. Look for Richard Widmark as the head of surgery at the hospital and Tom Selleck in a small role as a patient. In an interesting side note, the executive producer of the film is Martin Erlichman, Barbra Streisand's manager.
This film was a big hit when it was released and there's a lot of media of it out there - it's on DVD, VHS, laser disc... the soundtrack is even available. That being said, it sort of flies under the radar. It's infrequently screened on TV, and is rarely talked about. Still, it's remembered by many as a favorite. The trailer is above, uploaded to YouTube by augustotrek. The poster above is available on MoviePosterShop.com
Obscurity factor: 2 (easily found on many types of media, rarely screened or discussed)