The book is a cooperative effort of the members of the Rochester Desert Unit. It deals with body heat exchanges, sweat formation and water turnover in a general way, and then turns to specific problems of life in the desert. Rates of sweating, urinary excretion, fluid intake, water requirements and water shortage are discussed. Then come chapters dealing with various aspects of dehydration, on survival without drinking water in the desert, and on the water losses of men on life rafts. In a chapter comparing tropical with desert conditions there is a useful discussion of the physiological assessment of environmental stress. For comparing the stresses imposed by desert and tropical environments, the authors use as their index: the rate at which the body gains heat from the environment.