For several decades it has been assumed that higher testosterone (T) leads to greater growth of benign and malignant prostate tissue, but this view has come under greater scrutiny over the last several years. Although there are as yet no large-scale, long-term controlled studies of T therapy to provide a definitive assessment of risk, numerous smaller clinical trials as well as population-based longitudinal studies consistently fail to support the historical idea that T therapy poses an increased risk of prostate cancer or exacerbation of symptoms due to benign prostatic hyperplasia. This lack of prostate risk despite increased serum T appears to be explained by data showing that exogenous T does not raise intraprostatic concentrations of T or dihydrotestosterone, suggesting a saturation model. In contrast, there is mounting evidence that low serum T is associated with greater prostate cancer risk, and more worrisome features of prostate cancer. In conclusion, the available evidence strongly suggests that T therapy is safe for the prostate. Given that the population at risk for T deficiency overlaps with the population at risk for prostate cancer, it is strongly recommended that men undergoing T therapy undergo regular monitoring for prostate cancer.