Postoperative patients (42), each with demonstrable failure of 2 or more vital organ systems, were studied as they define a syndrome of multiple organ failure. They typify the emerging clinical entity of patients kept alive solely by reason of specific mechanical and pharmacologic support. Trauma initiated hospitalization in 40% and major bleeding, in 11%. Sepsis was judged to be of etiologic significance in 69%. Complications in clinical management were, in retrospect, thought to be of contributory etiologic significance in 57%. Of 42 patients, 29 died, a mortality of 69%. Mean duration of multiple organ failure was 30.5 days. Scientific, social, moral, ethical and legal factors emphasize the need to establish a statistically valid large data base concerning this new man-made syndrome which has both important scientific and social implications.