We present the dietary epidemiology of bladder cancer while controlling for a number of lifestyle and environmental risk factors in a study of 351 white male cases with histologically confirmed transitional cell carcinoma of the bladder and 855 white male controls selected from Erie, Niagara, and Monroe counties of western New York from 1979 to 1985. Usual diet was estimated by comprehensive interviews with use of a detailed food frequency questionnaire. An increased risk of bladder cancer was associated with higher kilocalorie intake, but only among those under 65 years of age, with the strongest pattern associated with fat intake. Further analyses of fat, carbohydrates, and protein, with adjustment for total kilocalories, resulted in a positive association of risk with fat intake and a decreasing risk with higher protein intake. Of the vitamins, carotenoid consumption appeared to decrease risk with increased consumption for those under 65 years of age. No significant differences between cases and controls were seen for intake of calcium, retinol, thiamin, riboflavin, niacin, vitamin C, vitamin D, and vitamin E. After adjustment for kilocalories and other confounders, higher intake of dietary sodium was associated with increased risk among both age groups, and the trends were statistically significant. The importance of diet in the etiology of bladder cancer is suggested by our findings.