Active rewarming of the hypothermic patient can be assisted by the inspiration of warmed, fully saturated gases and the administration of heated intravenous fluids. Utilization of a heated humidifier can be instigated quickly and permits flexibility in the amount of heat delivered to the thorax, through requiring continuous monitoring of airway temperature. A case is reported in which use of these techniques was associated with “rapid” rewarming, and some of the problems involving hypothermia and acidosis are discussed.