Risk factors of bladder cancer development were studied in a population-based case-control epidemiological study performed in Moscow. Relative risk (RR) indexes appeared to be increased in smokers (4.2) and ex-smokers (3.5) with statistically significant trends for two most important factors such as duration of smoking and duration of withdrawal. A pronounced although insignificant increase in the RR indexes was established for drivers (3.0) and a slight insignificant rise-for gas arc welding operators (1.5). The indexes were increased in subjects with a family history of cancer. The relative risk of cancer was significantly lower in beta-carotene consumers. A preventive effect of polyunsaturated fatty acids and oil and margarine used for frying was established. Risk of bladder cancer tended to increase with a rise in dietary protein. A dose-effect type inhibition of advancement of the disease by vitamin C was observed.