A case of heat stroke is described in which the patient presented comatose with a rectal temperature exceeding 42.5 degrees C. Standard external evaporative cooling and iced gastric lavage failed to alter his temperature or mental status. Iced peritoneal lavage brought about a decrease in rectal temperature to 39.4 degrees C and significant improvement in mental status. The patient recovered uneventfully. Techniques of rapid cooling are discussed.