The findings in this report of a deficit in mortality from cardiovascular diseases and an excess in diseases of the digestive system among open hearth workers indicate the need for further study of men working in hot environments. In future reports we hope to refine the comparisons by obtaining data which will enable classification of workers more precisely by intensity and duration of exposure within the open hearth. Of particular importance in future work are the evaluation of possible relationships between the actual levels of heat exposure and subsequent morbidity and mortality, as well as possible interactions between heat stress and physical exertion in terms of the incidence of heart disease and other select diseases.