Whereas case-control studies have been very consistent in suggesting a positive association between intake of dietary fat, especially animal fat, and prostate cancer, the results from past cohort studies have been mostly inconclusive. In this study, we evaluated consumption of high-fat animal products, raw vegetables, and fresh fruits, as well as obesity, smoking, and drinking, in relation to subsequent occurrence of prostate cancer. We studied a cohort of 20,316 men of various ethnicities interviewed between 1975 and 1980 in Hawaii. As of December 1989, 198 incident cases with invasive prostate cancer were identified by computer-assisted linkage of this cohort to the statewide Surveillance, Epidemiology, and End Results registry. Relative risks (RRs) for prostate cancer computed by proportional hazards regression were elevated for intake of beef [RR for highest to lowest tertile of intake = 1.6; 95% confidence interval (CI) = 1.1–2.4] and milk (RR = 1.4; 95% CI = 1.0–2.1), and for a summary variable for intake of high-fat animal products (RR = 1.6; 95% CI = 1.0–2.4). Weight was not consistently associated with prostate cancer, but there was an association with height (>167 cm) (RR = 1.8; 95% CI = 1.0–3.2 for the third and fourth quartiles relative to the lowest quartile in height). These associations were stronger in men diagnosed before age 72.5 years. The risk estimates for raw vegetable and fresh fruit intakes were close to 1.0. Smoking and alcohol drinking appeared to be unrelated to risk. This study provides further evidence for a role of animal fat in the etiology of prostate cancer and indicates that it may act by shortening the latency period of the disease.