We observed a 16-month-old infant with residual brain damage following a heat stroke from being left in a parked automobile. In contrast with adults, in whom heat stroke usually follows strenuous exercise, the condition in infants usually results from excessive environmental temperature and/or dehydration. Early recognition of the illness is imperative. Three cardinal freatures are hot, dry skin, central nervous system disturbance, and hyperpyrexia. Immediate treatment should be aimed at improving circulation with volume expanders and rapid cooling. Other supportive measures may be necessary to control seizures, renal failure, hematologic abnormalities, or hepatic involvement.