This paper reports results from a case-referent study on bladder cancer being conducted in parts of West Yorkshire; 991 cases have been incorporated in the results to date. Overall there was a significant risk of bladder cancer associated with smoking cigarettes. This habit showed a risk ratio of 1.8 (95% confidence limits of 1.5-2.3) for males. In addition there were significant overall risks associated with certain occupations; these include process workers in the dye manufacturing industry, who had a risk of 2.9 (95% confidence limits of 2.0-4.3) for males. When smokers were contrasted with nonsmokers, however, the risk was 4.6 for dye manufacturing process workers who smoked, while for nonsmokers the risk was much less at 1.9.