As with the original Prostate Cancer Prevention Trial, the use of a 5-ARI, in this case finasteride, was seen to reduce the incidence of prostate cancer by about a third. Although high-grade cancer was more common in the 5-ARI group, after 18 years of follow-up there was no significant difference in rates of prostate cancer specific survival or overall survival between the two groups. Prescription of finasteride or dutasteride as a chemopreventive agent against prostate cancer cannot be justified on the available evidence. [With external links to current evidence and summaries]