This chapter discusses the diagnosis, evaluation and management of hypothermia. Hypothermia is confirmed with rectal thermometer, indwelling Foley with temperature sensor, or other means of core temperature measurement. In general, hypothermia is a clinical diagnosis. However, laboratory tests may be helpful to look for an underlying condition that causes a patient to become hypothermic. Cardiopulmonary bypass has been used in some cases of severe hypothermia to rewarm patients and provide circulatory support. All patients with moderate to severe symptomatic hypothermia should be admitted to the hospital for rewarming and observation. Patients with mild hypothermia who are otherwise healthy can be rewarmed in the emergency department. Deteriorating hypothermic patients need to have their airway managed. There is no contraindication to performing rapid sequence induction (RSI) with the usual drug regimen in these patients.