Prostate cancer is the number 1 cancer killer among Puerto Rican (PR) men. Plant foods have been inversely associated with prostate cancer. Legumes play a significant role in the PR diet; consumption of legumes in PR (14 lb/capita) was double that of the United States (7 lb/capita). We examined dietary protein consumption (from baseline 24-h dietary recalls) and prostate cancer mortality in the PR Heart Health Program, a cohort study of 9,824 men aged 35-79 years at baseline (1964) with follow-up until 2005. Total protein intake in the cohort was 85 g/day, and sources of protein were 30% vegetable, 30% dairy, 31% animal, and 8% seafood protein. Legume intake was 2.3 servings/day (1/4 cup each). Legume intake was not associated with prostate cancer mortality [comparing highest quartile to lowest quartile-odds ratio (OR) 1.40 [95% confidence interval (CI) 0.91-2.18], P trend 0.17]-nor were total protein, animal, seafood, dairy, or vegetable protein intakes. Consuming 1-2 servings of fruit was inversely associated (OR 0.50, 95% CI 0.32-0.77), whereas consuming more than 2 servings of fruit was not associated with prostate cancer mortality. Thus, we find no association between legumes or protein intake and prostate cancer mortality in this longitudinal cohort study of PR men.