Exercise-induced heat stroke is defined as core temperature greater than 104 degrees F (400 degrees C) accompanied by signs or symptoms of organ system failure, most commonly CNS dysfunction. Exertional heatstroke is a life-threatening emergency that requires immediate whole-body cooling for a satisfactory outcome. Cooling should be initiated and, in the absence of life-threatening complications, completed on site prior to evacuation to an emergency department or other facility. Cool-water immersion provides the fastest whole body cooling rate and the lowest morbidity and mortality for exertional heat stroke. When water immersion is unavailable, ice water towels combined with ice packs on the head, trunk, and extremities provide effective but slower whole-body cooling. Medications, including antipyretics and dantrolene, are not effective in treating heatstroke and should not be used. Clinical observations indicate that prognosis is closely linked to the amount of time a patient's temperature remains elevated. Prevention strategies are essential to reducing the incidence of exertional heatstroke, heat exhaustion, and exercise-associated muscle cramping.