Androgen deficiency of the ageing males has become a topic of increasing interest because demographic data demonstrate the increasing percentage of the population of older men. Testosterone Deficiency Syndrome (TDS) is a clinical and biochemical syndrome associated with the advancing age and characterized by symptoms and a deficiency in serum testosterone levels and/or action. Testosterone concentration falls progressively with age and a significant percentage of men over the age of 60 years have serum testosterone levels below the lower limits of young adult men. However, pathogenesis and incidence of this phenomenon are still not clearly known, what is associated with a lack of clear diagnostic criteria, especially with not established lower reference limit of normal testosterone serum levels. Recent years have brought evidence of benefits of testosterone replacement therapy of hypogonadal men but long-term interventional studies on the effects of testosterone treatment in the older men on the cardiovascular risk and mortality are still limited. Available data are inadequate to determine the safety of testosterone replacement therapy and optimal serum testosterone levels.