We report one case of severe accidental hypothermia; rectal temperature was 25 degrees C. Hypoxemia unmodified by 100 O2 inhalation in an ordinary face-mask was easily corrected using a face-mask CPAP; a ventilation-perfusion mismatching could be implicated in the cold induced hypoxemia. Active rewarming (1.5 degrees C/h) was pursued from 25 to 37 degrees C, using non aggressive methods: warming blankets and a Bennett heated humidifier inserted in the CPAP system. Even in severe hypothermia successful results may be obtained without resort to sophisticated methods.