A case-control study of 371 prostate cancer patients and comparable control subjects admitted to Roswell Park Memorial Institute (RPMI), Buffalo, New York, was conducted. Data were obtained from routine epidemiologic questionnaires administered to all patients on admission. An index of beta-carotene intake was computed based on the vitamin A activity of 27 fruits and vegetables included in a food frequency checklist. A similar measure of fat intake from meats was computed based on nine meats included in the checklist. Intake frequencies of common and alcoholic beverages also were studied. A significant age-adjusted and residence-adjusted protective effect for high levels of beta-carotene intake was observed (relative risk [RR], 0.60; 95% confidence interval [CI], 0.37 to 0.99). This effect was evident particularly among men 68 years of age and younger (RR, 0.30; 95% CI, 0.13 to 0.66), but not among subjects older than 68 years of age. A trend toward increased risk for fat intake was not significant. However, the reported usual consumption of high-fat milk was associated with increased risk (RR, 1.92; 95% CI, 1.05 to 3.50). A greater reported frequency of whole milk intake was similarly associated with increased risk. Men who reported drinking three or more glasses of whole milk daily had an RR of 2.49 (95% CI, 1.27 to 4.87), compared with men who reported never drinking whole milk. When these findings are evaluated in the context of other recent studies, the weight of the evidence appears to favor the hypothesis that animal fat intake is related to increased risk of prostate cancer.