This longitudinal study began in 1984 and built on college data from entrance physical examinations, social and athletic records for 1916-1950, self-assessed mail questionnaire responses on six occasions from 1962-1980 and death certificates from 1916 to date. A seventh lifestyle and health questionnaire was sent to living alumni in 1988. Exercise findings gathered from this and former questionnaires were converted into a physical activity index on the basis of estimated energy output ratings expressed in kilocalorie per unit of time and kilocalorie per kilogram per unit of time. The 1988 questionnaire preserved comparability with earlier observations but allowed assessment of endurance, body weight, standard caloric values of specific physical activities, and intensity and frequency of effort. It was felt that such distinctions would aid an attempt to devise exercise prescriptions for men of differing ages and conditions of health. To obtain current and historical medical data on alumni, permission was requested of the study subjects to contact personal physicians. Results of physical examinations completed by staff in 1962-1965 were provided to personal physicians of study subjects. Similar results were provided to personal physicians of alumni undergoing treadmill and clinical testing in 1988.