Understanding the role of testosterone replacement therapy (TRT) in the development and progression of prostate cancer is an important concept in treating patients with symptoms of hypogonadism. This article revealed a small number of mostly retrospective, observational studies describing the use of TRT in the general population, in men with prostatic intraepithelial neoplasia (PIN), in men with a history of treated prostate cancer, and in men on active surveillance for prostate cancer. The current literature does not report a statistically significant increase in the development or progression of prostate cancer in men receiving testosterone replacement for symptomatic hypogonadism, and the prostate saturation theory provides a model explaining the basis for these results. The use of TRT in men with a history of prostate cancer is considered experimental, but future results from randomized controlled trials could lead to a change in our current treatment approach.