A case-control study among 574 male and 158 female bladder cancer patients and equal numbers of matched controls was conducted between 1969 and 1974 in 17 hospitals in six United States cities. We determined that cigarette smokers of both sexes were at higher relative risk than nonsmokers. Cigarette smoking was responsible for about one-half of male and one-third of female bladder cancer. There was an excess of bladder cancer patients with some previous occupational exposure, such as rubber, chemicals, and textiles. A weak association with coffee drinking, which appeared to be independent of smoking, was found for males. Users of artificial sweeteners were not over-represented among the cases. The authors conclude that the epidemiologic pattern of bladder cancer cannot be fully accounted for by cigarette smoking and occupational exposure and suggest a series of metabolic studies to assess the role of additional factors, such as nutrition.