Androgens have a profound effect in male sexual function in general and erectile physiology in particular. Despite the common belief that male sexuality is fully dependent on normal androgens, hypogonadal men are capable of sexual erections; almost a third of men receiving effective antiandrogen therapy can develop erections when tested with an erotic challenge. However, successful hormonal supplementation that results in normal testosterone values does not always restore libido and erectile function. Although the primary goal of treatment for hypogonadism may be to restore sexual function, there will be other significant benefits and potential drawbacks. Libido, general well-being, osteoporosis, muscle strength, mental acuity, and growth hormone levels will all be positively affected by appropriate management of low testosterone levels. Testosterone replacement therapy should maintain not only physiological levels of serum testosterone but also its metabolites, including dihydrotestosterone and oestradiol. The assessment of hypogonadism, its treatment and monitoring, are unavoidable responsibilities of the urologist.