The May 1986 Mt. Hood climbing disaster presented Portland area hospitals the opportunity to initiate a trial of extracorporeal rewarming using cardiopulmonary bypass in ten severely hypothermic patients (two survivors). The data from this experience as well as others previously reported can yield prognostic indicators of survival in cases of accidental hypothermia. These are demonstrated to include: the presence of underlying medical illness, duration of cold exposure, initial core temperature, mental status, the presence of spontaneous respirations, presenting cardiac rate and rhythm, and arterial oxygen tension. Profound hyperkalemia and markedly elevated serum ammonia levels indicate cell lysis; significant hypofibrinogenemia suggests intravascular thrombosis and each laboratory marker predicts a dire outcome. The treatment of choice for severe accidental hypothermia is felt to be rapid core rewarming on cardiopulmonary bypass.