A program, covering the principal factors affecting man's physiological and behavioral response to his thermal environment and their implications for his health, consists of three projects: #1. CHARACTERIZATION OF MAN'S THERMAL ENVIRONMENT: rational environmental indices of environmental stress and strain will be developed based on direct measurement of heat and mass transfer characteristics of the thermal environment. #2. PHYSIOLOGICAL RESPONSES TO WARMTH AND HUMIDITY: A standardized test for thermoregulatory efficiency will be developed based on studies of temperature regulation in warmth and response to acclimation by exercise and heat. #3. PHYSIOLOGICAL RESPONSES TO THE COLD: Control of shivering metabolism, cold acclimation and corresponding role of age, sex, length of exposure, and physical condition will be studied with emphasis on moderate cold. BIBLIOGRAPHIC REFERENCES: Nishi, Y., R.R. Gonzalez and A.P. Gagge. Prediction of equivalent environments by energy exchange and assessments of physiological strain and discomfort. Israel J. Med. Sci. 12: 808-811, 1976. Nishi, Y. and A.P. Gagge. Effective temperature scale useful for hypo- and hyperbaric environments. Aviation, Space, and Environmental Med. 48: 97-107, 1977.