The increasing population of elderly men means there is also an increase in those suffering from late-onset hypogonadism and testosterone deficiency, with all its attending consequences such as reduced libido, erectile dysfunction, metabolic disturbances, cardiovascular disease, decreased bone density and reduced quality of life. The use of testosterone replacement therapy may benefit such patients but remains controversial, especially with regard to the risk it may have on prostate cancer. However, there is no conclusive evidence that testosterone therapy increases the risk of developing prostate cancer nor is there any evidence to suggest that it can convert subclinical or indolent prostate cancer into a clinically significant one. In fact, a number of recent reports have shown that it is safe to give testosterone therapy in patients who have been successfully treated for early prostate cancer. Therefore, the purpose of this review is to discuss the role of testosterone replacement therapy, focusing on those with prostate cancer, as well as the risks and benefits that every physician must consider before commencing treatment.