Exertional heatstroke (EH) occurs when heat production, generated by muscular exercise, exceeds the body's heat dissipation capacities. This illness has been reported among young, active individuals, laborers, and religious pilgrims. Although EH includes a rectal temperature above 39.5 degrees C (depending on the timing of the measurement) and elevation of serum enzymes, altered mental status is the universally accepted sign which distinguishes EH from heat exhaustion. Once EH is suspected, cooling therapy should be initiated immediately and investigation of multiple-system involvement should be undertaken. Delay in diagnosis occurs more commonly in moderate environments, when suspicion of EH is low. Complications of EH include the central nervous, cardiovascular, pulmonary, and gastrointestinal systems, often with renal and hematologic involvement. Treatment at the point of collapse should focus on clearing the airway, measurement of rectal temperature, whole body cooling, intravenous therapy, and prompt evacuation. Hospital treatment should emphasize whole body cooling, control of convulsions, monitoring of acid-base status, cardiac function, and renal function. The incidence of EH has been reduced markedly in Israel, by using the following simple guidelines: rest periods during exercise in heat, medical monitoring of strenuous activities, use of meteorological indices, and evaluation of medical history.