Articles published in peer-reviewed journals between January 1983 and June 1994 were reviewed for inclusion in a meta-analysis designed to estimate the relative risk of prostate cancer in farmers. Three analyses were performed: (1) an analysis including all articles written during the specified time period that listed an estimate of the relative risk of prostate cancer in farmers: (2) an analysis that included only retrospective studies; and (3) an analysis that included only studies reporting a standardized mortality ratio. Positive associations between prostate cancer and farming were found by the analysis including all studies and the analysis limited to the retrospective studies. No association was found with the analysis that included only studies reporting a standard mortality ratio. The most plausible explanation for the positive association between prostate cancer and farming is exposure to hormonally active agricultural chemicals.