OBJECTIVES: To examine the relationship of insulin, glucose, and anthropometry with the subsequent risk of prostate cancer. METHODS: The relative risk of prostate cancer by insulin, glucose, and anthropometric measures was evaluated in 823 male participants (87 patients with prostate cancer in 10,737 person-years of follow-up) of the Baltimore Longitudinal Study of Aging who had at least one fasting plasma insulin measurement, which was prediagnostic for those with prostate cancer. Age-adjusted and multivariate-adjusted relative risks were estimated from Cox proportional hazards regression models. RESULTS: Insulin concentrations were in the normal range (defined as less than 20 microU/mL) for 95.1% of participants. Fasting insulin and glucose levels were unrelated to prostate cancer risk in our overall analysis (P for trend = 0.56 and 0.45, respectively). The relative risk of prostate cancer for the second through fourth quartiles of the waist/hip ratio compared with the lowest quartile was 2.10, 1.96, and 2.06, respectively (P for trend = 0.32). Risk was unrelated to waist circumference and body mass index. CONCLUSIONS: The results of this study do not conclusively support positive associations of markers of insulin and glucose metabolism and obesity with prostate cancer. Additional larger prospective studies with repeated measure of these parameters are warranted to explore these associations further.