A 27-year old female was discovered at 4 a.m. lying in a wet field, the ambient temperature being of 4 degrees C. Her rectal temperature had fallen to 19 degrees C. She was comatose and failed to respond to noxious stimuli. Her pupils were dilated and fixed. Her respiratory rate was reduced to three to four breaths per min. Her blood pressure was not measurable and neither femoral or carotid pulse could be detected. The heart was in sinus rhythm with a rate of 40 b X min-1. During her transfer to hospital, she was ventilated with oxygen, a tidal volume of 300 ml and a rate of 10 b X min-1. On arrival in the emergency room, a short period of ventricular fibrillation preceded cardiac arrest. Cardiac massage and sodium bicarbonate infusion were continued during the transfer of the patient to the operating theatre. A femoro-femoral cardiopulmonary bypass was started with a bloodless priming, 3 mg X kg-1 heparin and a flow of 3,000 to 3,500 ml X min-1. Mean arterial pressure was maintained between 65 and 85 mmHg; cardiac massage was discontinued during the bypass. Within 50 min, ventricular fibrillation appeared, rectal temperature had increased to 33 degrees C. Electrical defibrillation (300 J) was successful. Cardiopulmonary bypass was stopped after 63 min. The postoperative course was uneventful, apart from transient pulmonary oedema. At the time of discharge, a week later, no loss of intellect or change in behaviour could be perceived.(ABSTRACT TRUNCATED AT 250 WORDS)