This interdisciplinary study of deals with the contribution of psychological factors to biological responses in a life stress situation. The study focused on a group of normal adult males in a situation of severe training- as army paratroopers. Changes in their biological responses reveal the importance of coping, a psychological process, in modifying the body's response to stress. The relevance of these results to health and disease in general populations is extensively discussed. Psychobiology of Stress has broad implications for psychiatrists, internists, clinical psychologists, endocrinologists, as well as persons in environmental medicine, personnel selection, aviation, and parachuting.