Statin drugs appear to protect against advanced and possibly high-grade prostate cancer, perhaps through cholesterol-lowering. Thus, we evaluated the association between plasma cholesterol and prostate cancer. We conducted a prospective study in the CLUE II cohort of Washington County, MD. Included were 6,816 male county residents aged 35+ years old who did not have a cancer diagnosis at baseline in 1989. Plasma cholesterol, measured enzymatically at baseline, was categorized by clinical cutpoints. Cox proportional hazards regression was used to estimate multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI) for total (n = 438) and high-grade (Gleason sum > or =7, n = 137) prostate cancer. Compared to men with high cholesterol (> or =240 mg/dl), men with desirable (<200 mg/dl) or borderline (200 to <240 mg/dl) levels were less likely to develop high-grade prostate cancer, particularly when restricting to organ-confined cases (HR: 0.68, 95% CI 0.40-1.18; P trend = 0.12) and among men with higher BMI (HR: 0.36, 95% CI 0.16-0.79; P trend = 0.02). Results were unchanged after excluding cholesterol-lowering drug users. Cholesterol was not associated with total prostate cancer. Our study supports two prior ones suggesting that cholesterol influences risk of high-grade prostate cancer, and indirectly supports the hypothesis that cholesterol-lowering is a mechanism by which statins are protective.