PIP: A 1993 editorial in "Fertility and Sterility," accompanying publication of two cohort studies by Giovannucci et al. indicating a positive association between vasectomy and prostate cancer, noted the observed association could have resulted from chance, bias, or a causal association. There is strong potential for bias in the selection of study participants and in the additional medical attention received by sterilized men. Men who undergo vasectomy may have different life-style characteristics than those who do not. Meta-analyses of prostate cancer risk have calculated higher odds ratios in studies judged to have inadequate selection of controls and possible detection bias than in more methodologically rigorous studies. Overall, a review of the research evidence reveals inconsistent study findings, weak strength of any observed association, and little biologic plausibility for a vasectomy-prostate cancer link.