In a population-based case-referent study of urothelial cancer in Stockholm during 1985-87, information was obtained from 80% of 320 identified male cases and 79% of 363 selected male referents. Industrial exposures were assessed for each subject by an industrial hygienist on the basis of questionnaire data. Exposure to benzene (any annual dose) gave a relative risk (with 95% confidence interval) of 2.0 (1.0-3.8). The highest risk was seen for a high annual dose. Subjects exposed to both diesel and petrol exhausts (moderate/high annual dose) had a relative risk of 7.1 (0.9-58.8). However, adjusting for benzene changed the relative risk to 5.1 (0.6-43.6). It might be rewarding to consider whether benzene from petrol confounds the associations previously suggested between exhausts and urothelial cancer. Exposure to polychlorinated biphenyls (PCB) gave a relative risk of 3.3 (0.6-18.4).