Serum testosterone levels peak in early adulthood in men and fall progressively with age. Since sex hormone binding globulin increases with age, the unbound forms of testosterone (free and bioavailable testosterone) fall more steeply than total testosterone levels. Serum testosterone levels below the normal range for young healthy adult males provide chemical evidence of androgen deficiency independent of the age of the patient. When accompanied by signs or symptoms that are compatible with androgen deficiency, treatment with testosterone should be considered in older men without evidence of prostate or breast cancer. While such therapy for younger hypogonadal men has shown benefit on libido, mood, muscle mass, muscle strength, bone mineral density and haematocrit, similar benefits in older men have not been as adequately assessed. While there is no convincing evidence that testosterone treatment in older men will increase the risk of cardiovascular or prostate cancer, long-term, well-controlled studies are lacking and needed. Treatment options for older men include injectable, transdermal and transbuccal testosterone preparations.