The number of men for whom testosterone is prescribed is rapidly increasing. The aging man normally demonstrates a gradual decline in testosterone. Symptoms of hypogonadism include erectile dysfunction, diminished libido, sarcopenia, increased adiposity, osteopenia and osteoporosis, impaired cognition, and depression. There is a paucity of data regarding both efficacy and safety of testosterone replacement therapy. Testosterone levels have been shown to modulate prostate cancer risk and progression. A prospective evaluation of prostate cancer risk with testosterone replacement therapy has not been conducted. We outline concerns and recommendations for the use of testosterone replacement therapy in the aging man.