The Influence of Finasteride on the Development of Prostate Cancer” (New England Journal of Medicine, Vol. 349, No. 3, pp. 215–224), I. Thompson et al. reported the results of a major study to examine the effect of finasteride in reducing the risk of prostate cancer. The study, known as the Prostate Cancer Prevention Trial (PCPT), was sponsored by the U.S. Public Health Service and the National Cancer Institute. In the PCPT trial, 18,882 men 55 years old or older with normal physical exams and prostate specific antigen (PSA) levels of 3.0 nanograms per milliliter or lower were randomly assigned to receive 5 milligrams of finasteride daily or placebo. At 7 years, of the 9060 men included in the final analysis, 4368 had taken finasteride and 4692 had received placebo. For those who took finasteride, 803 cases of prostate cancer were diagnosed, compared with 1147 cases for those who took placebo. Decide, at the 1% significance level, whether finasteride reduces the risk of prostate cancer. (Note: As reported in an issue of the Public Citizen’s Health Research Group Newsletter, most of the detected cancers were “low-grade cancers of little clinical significance.” Moreover, the risk of highgrade cancers was determined to be elevated for those taking finasteride.)