Owing to the demographic development, the aging male will require more consideration in future. In contrast to a rapid decline of estradiol during menopause in women, the process of aging in the male is retarded and subject to high individual variations. Impairment of spermatogenesis is observed as a continuous process occurring over decades. However, only about 50 % of men in their eighties show complete loss of fertility. In principle, spermatogenesis may be retained well into senescence. Of importance for the individual health condition is the fact that the number of Leydig cells declines with advancing age. Thus, altered sex hormone concentrations in aging men result from both functional disturbances and a gradual reduction in Leydig cells. Furthermore, an impaired feed-back mechanism of the pituitary-gonadal axis occurs, with disappearance of the circadian testosterone (T) rhythm. LH and FSH levels are increased, and a reduced bioavailability of sex hormones is observed. Lower total testosterone concentrations in men over 60 years are accompanied by clinical signs of reduced virility, such as decreased muscle mass and strength as well as reduced sexual hair growth and libido. An age-related decline in androgen secretion and plasma testosterone levels therefore suggests the use of androgen supplementation. However, there is a lack of risk-benefit long-term studies. Increased research in the male is mandatory to meet the requirements of the aging population. This should include the availability of precise epidemiological data about the frequency of partial androgen deficiency in aging males (PADAM).