Vigorous exercise is currently being encouraged for health maintenance. There is much evidence that a moderate amount of exercise is needed for the maintenance of functional integrity of the cardiovascular system, muscles, bones, and ligaments. There is also fragmentary evidence of a preliminary nature suggesting that regularly performed exercise may protect against and have beneficial effects on coronary artery disease, diabetes, and hypertension. However, the scientific evidence that strenuous exercise has long-term health benefits or slows aging is meager and unconvincing. Even in the case of coronary artery disease, diabetes, and hypertension, the majority of studies have provided either negative or inconclusive results or have resulted in only minor improvements. Taken together, available evidence is inadequate to serve as a basis for recommending regular participation in strenuous exercise for middle-aged and older individuals. This is particularly true because the theories that exercise may accelerate the aging process as a result of increases in metabolic rate and stress hormone production have never been disproved. Therefore, because of the major public health implications of exercise, large-scale, well-controlled studies of the effects of exercise on coronary artery disease, adult onset diabetes, hypertension, and various aspects of the aging process are urgently needed. Important barriers to progress in this area are the current dearth of exercise physiologists interested in research on health maintenance and well trained in human exercise physiology and the lack of an appropriate research funding mechanism for large-scale, interdisciplinary studies of the effects of exercise on chronic disease processes and aging.