Laboratory data implicate cadmium as a prostate carcinogen. However, epidemiological studies concerning the association between cadmium and prostate cancer are inconclusive. This article reviews the epidemiological literature on cadmium and prostate cancer with a special focus on highly exposed occupational cohorts. We searched the MEDLINE database from 1966 to 2002 for articles on cadmium and prostate cancer. All published analytical and descriptive studies that included relevant data were reviewed. In addition, we reviewed the experience of cohorts highly exposed to cadmium in nickel-cadmium battery plants. Of 4 descriptive studies, 3 reported a positive association between cadmium and prostate cancer. Of 10 case-control studies, 5 (50%) reported a positive association. Of 11 cohorts studies, 3 (33%) found a positive association. Finally, 4 studies on cohorts exposed in occupational nickel-cadmium batteries were identified and analyzed. The summary score of the standardized mortality ratios (SMRs) was weakly but not significantly positive 126 (95% confidence interval C.I.: 83-184). In contrast to laboratory studies, epidemiological studies do not convincingly implicate cadmium as a cause of prostate cancer. Future epidemiological studies that attempt to resolve the discrepancy between laboratory and epidemiological studies of cadmium carcinogenesis may benefit from incorporating biological measures of cadmium exposure.