Epidemiological studies have demonstrated that prevalence of hypogonadism in old males increases with every additional decade of life. These males present various symptoms including decrease of sexual function, decrease of cognitive function, altered lipid profile, increased visceral adiposity, changes in bone density and muscular strength secondary to atrophy Currently testosterone injections and gel preparations are the most used. Testosterone replacement therapy provides significant symptomatic improvements for men with late start hypogonadism. Long-term benefits and risks of testosterone replacement therapy will be more evident when testosterone effects are studied on all health related parameters over a prolonged period of time. There is a large ongoing multicentric randomized clinical trial sponsored by NIH for testosterone control in old men with low testosterone levels. Its results may give answers to the possible benefits and risks of testosterone replacement in aging males. If an aging male is diagnosed as late-start hypogonadism, the urologist should discuss with the patient potential benefits and risks of testosterone therapy Aging males with significant erythrocytosis, untreated sleep apnea, prostate cancer and high risk of cardiovascular events must be excluded from testosterone replacement therapy. Currently there are not enough evidences to clearly state that the benefits of testosterone replacement therapy in aging males are better than the risks of this treatment. A general recommendation cannot be given that testosterone replacement therapy may be applied to al aging males with low testosterone levels independently of significant signs or symptoms.