The present contribution reviews the epidemiological literature on the risk factors for bladder cancer in humans, pointing to the new leads from the available knowledge and to suggestions on prevention and research needs. Smoking accounts for about 50% of bladder cancer cases in western countries, occupational exposures are second in importance in bladder cancer development. Exposure to aromatic amines in dyestuff manufacture, in the rubber and textile industry, occupations entailing exposure to paints and solvents, leather dust, inks, some metals, PAH, combustion products and diesel exhausts have been identified as risk factors from epidemiological studies. Other investigations have detected increased risk for bladder cancer in association with dietary factors, specifically fats and cholesterol, and with contamination of drinking water by chlorination by-products.