The association of diet and smoking with bladder cancer was investigated in a cohort study conducted in Hawaii. The study included 7995 Japanese-American men who were born between 1900 and 1919, and were examined from 1965 to 1968. After 22 years of follow-up, 96 incident cases of bladder cancer were diagnosed. Current cigarette smokers had a 2.9-fold risk of bladder cancer, compared with nonsmokers. A direct dose-response relation was observed, based on pack-years of cigarette smoking. Consumption of fruit was inversely associated with the risk of bladder cancer (P = 0.038). The relative risk was 0.6 among subjects who had the most frequent (> or = 5 times/wk) intake of fruits compared to those with the least intake (< or = 1 time/wk). A weaker inverse association with milk intake was also observed (P = 0.07). Frequent consumption of fried vegetables, pickles, or coffee increased the risk of bladder cancer, but none of these foods showed a significant dose-response relationship. There was no association of other selected foods, alcohol, total calories, protein, fat, or carbohydrates with bladder cancer risk.