World-wide life expectancy at birth for men and women will have increased by about 20 y during 50 y period between 1950 and 2000. As a result, the proportion of the elderly population is expected to increase significantly in the 21st century. Despite this increase in longevity for men and women, men still have significantly shorter life expectancy of approximately 5 y. To further reduce and prevent debilitating disease and disability in elderly men, a question is whether any type of interventions, such as hormone replacement therapy, may play a role in improving the quality of life as proven in post-menopausal women. Men experience age-related decline of capability physically and mentally. Various symptoms, such as nervousness, depression, impaired memory, inability to concentrate, easy fatigability, insomnia, hot flushes, periodic sweating, reduction of muscle mass and power, bone ache, and sexual dysfunction, are related to this change. The fact that a number of age-related changes resemble features of various hormonal deficiency has led to worldwide interest in the use of various hormonal preparations in an effort to prevent the aging process in elderly men. Even though there have been opinions against hormonal supplementation in the aging male, preliminary studies defining the risk/benefit ratio of androgen supplementation appear to be encouraging. To understand testosterone supplementation in the aging male, this review will! discuss the following important topics: physiology of male hormonal balance, changes in reproductive organs in elderly men, endocrine evaluation of the male, pharmacological effects of testosterone on target organs, available preparations for testosterone, and testosterone supplementation.