Two fatalities from occupational heat stroke, and illness and death from environmental heat are discussed. In the first fatality, the subject was employed at a surface coal mine performing heavy labor in an outdoor dry bulb temperature of 39.4 degrees-C. He collapsed and was treated at a hospital. Cause of death was listed as systemic hyperthermia with extreme generalized dilation of capillaries and cerebral edema. In the second fatality, the subject was employed as a furnace attendant at an aluminum (7429905) foundry. He accidentally spilled molten aluminum on the floor and spent 15 minutes removing the spill while wearing a silver (7440224) reflective suit. Outdoor dry bulb temperature was 28.3 degrees; estimated temperature of the molten aluminum in the furnace was 982.2 degrees. The subject was discovered having seizures in the foundry parking lot. He was treated at a hospital. Causes of death were listed as hyperthermia, disseminated intravascular coagulation, and coronary arteriosclerosis. Illness and death from environmental heat in both indoor and outdoor settings are discussed. The health status of workers in determining the response to heat is discussed. Preventive measures, recommended in a criteria document for occupational exposure to hot environments, developed by NIOSH, are listed.