The recent increase in the elderly population, current health trends, and awareness of age-related changes in the male endocrine system have led to discussions about the endocrine system being a "pacemaker" of male aging. Better prevention and treatment of "non-beneficial states of health" in aging men, such as generally decreased well-being and virility, increased visceral fat, osteopenia, atherosclerosis, and impaired cognitive function, is based on improved understanding of aging, particularly the significance of age-associated hormonal changes. Although not as dramatic as in women, men also show declining hormone serum concentrations with aging (Vermeulen and Kaufinan, 1995). Because aging is associated with deleterious effects resembling the clinical signs of hypogonadism or states of subnormal hormone concentrations, the potential role of hormone supplementation in aging men paralleling hormone replacement therapy in postmenopausal women is the topic of discussion. The goal of hormone replacement would be to improve body composition and increase muscle strength and quality of life in men, thereby reducing mortality and morbidity. The findings so Ear support the need for long-term studies of hormonal supplementation in older males showing decreased hormone serum levels. Nevertheless, to date, such a use outside the context of a clinical trial is not justified. (C) 1999 Elsevier Science Inc. All rights reserved.