In a Canadian population-based case-control study of 480 males and 152 female case-control pairs, the relative risk for development of bladder cancer for ever used versus never used cigarettes was 3.9 for males and 2.4 for females, with a dose-response relationship in both sexes. A reduced risk was associated with the use of filter cigarettes compared to nonfilter cigarettes. After control for cigarette usage, a significant risk was noted for male pipe smokers. For male ex-smokers the risk after 15 years of no smoking was less than one-half that of current male smokers. Bladder cancer risk was found for workers in the chemical, rubber, photographic, petroleum, medical, and food processing industries among males and for workers occupationally exposed to dust or fumes among both sexes. Bladder cancer risk was elevated for males consuming all types of coffee, regular coffee, and instant coffee and for females consuming instant coffee, but no dose-response relationship was found. Risk was found for males consuming water from nonpublic supples but not for females. No risk was observed in males or females consuming nitrate-containing foods, beverages other than coffee, or fiddlehead greens. Hair dye usage in females and phenacetin usage in males and females carried no risk. Divergent findings by area for aspirin suggested that an overall association was not causal. Reevaluation of the data on artificial sweeteners confirmed a significant bladder cancer risk in males and a dose-response relationship. The cumulated population attributable risk for bladder cancer was 90% for males from cigarette smoking, industrial exposure, and exposure to nonpublic water supplies and 29% for females from cigarette smoking, industrial exposure, and instant coffee consumption.