The biological bases of endocrine alterations in ageing men are now well identified: progressive impairment of testicular function, decline in growth hormone (GH) secretion with decreased insulin-like growth factor-I (IGF-I) levels, and reduced adrenal androgen secretion. Insulin resistance and glucose intolerance also accompany male ageing. The mechanisms of these age-related changes are still unknown. There are preliminary results on the effects of hormonal replacement therapy in older males with mild hypogonadism or decreased IGF-I levels. Controlled placebo studies will in the future define the risks and benefits of long-term administration of androgens, GH or GH-releasing hormone in these patients. In view of the severe potential side effects, the generalized use of hormonal substitution in elderly men cannot, for the moment, be recommended.