The concerns about testosterone therapy in ageing men with late-onset hypogonadism mainly address the risk of prostatic disease, i.e. either benign prostatic hyperplasia (BPH) or prostate cancer (PCa). Both conditions are highly dependent on androgen action and recent clinical data on the cancer-preventive effect of the 5alpha-reductase inhibitor finasteride have supported the possible role of androgens in PCa. However, the clinical data especially on the long-term effects of exogenous androgen substitution in regard to prostate safety are nonconclusive in many respects. As sufficient clinical studies on these risks will not be available in the near future, the approach of testosterone therapy towards prostate complications should be kept on a safe but practical basis. This review includes some recommendations in regard to testosterone therapy and prostate monitoring in patients with BPH and bladder outlet obstruction, with previous history of curative treatment for PCa or with prostatic intraepithelial neoplasia.