Hypothermia occurs commonly in severely injured patients and is associated with a high mortality rate. It perturbs the normal homeostatic response to injury and affects multiple organ systems and physiologic processes. In trauma patients, hypothermia-induced coagulopathy often leads to marked bleeding diathesis and frequently provides a challenge for the surgeon. Once hypothermia occurs, it is often difficult to correct. Efforts to prevent and treat hypothermia in trauma patients should be instituted in the field and continued as an integral part of the resuscitation process. Hospital personnel and physicians at various levels caring for trauma patients from the initial injury and thereafter should bear in mind that a patient's temperature is as important as any other vital sign. Appropriate measures for preventing and treating hypothermia should be instituted promptly and tended to with utmost vigilance.