As new guidelines on the use of 5-alpha-reductase inhibitors (5-ARIs) for prostate cancer chemoprevention produced by the American Society of Clinical Oncology (ASCO) and American Urological Association (AUA) have recently been published, the use of 5-ARIs is becoming of increasing interest. We analyzed the current evidence to support the use of 5-ARIs in the prevention of prostate cancer. We therefore compared the new guidelines of the ASCO and AUA with the current data concerning the use of 5-ARIs in the prevention of prostate cancer. At present, there is still an open debate going on whether or not it is advisable to incorporate the use of 5-ARIs as chemopreventive agents in daily practice.