Hypogonadism is highly prevalent in older men and men who have prostate cancer. The symptoms of hypogonadism, such as depression, decreased libido, erectile dysfunction, and decreased bone mineral density, can significantly impair a man's quality of life. Moreover, we know that testosterone plays an important role in erectile preservation and in the growth and function of cavernosal and penile nerves. There are compelling data to suggest that testosterone replacement therapy (TRT) in normal and high-risk men does not increase the risk for prostate cancer. In the few studies of men treated with TRT after a radical prostatectomy, there have been no biochemical recurrences. Based on these data, it is difficult to justify withholding TRT following a radical prostatectomy. If we do not lower the testosterone levels of eugonadal men after a radical prostatectomy, how can we justify not replacing testosterone levels in hypogonadal men to make them eugonadal following a radical prostatectomy?