Three patients, two men aged 47 and 33 years and a woman aged 33 years, became hypothermic after an accident with body temperatures of 34.5, 26.2 and 23.1 degrees C, respectively. Two of them developed circulatory disorders, for which reanimation was performed. All three patients recovered after active external heating using among other things warmed infusion fluids, a warmed waterbed, continuous arteriovenous rewarming and rewarming with the heart-lung machine. For the treatment to be successful, the type of rewarming selected should be guided by the degree of hypothermia, the circulatory situation and the severity of the accessory injuries.