Tobacco smoking is the main known cause of urinary bladder cancer in humans. In most populations, over half of cases in men and a sizeable proportion in women are attributable to this habit. Epidemiological studies conducted in different populations have shown a linear relationship between intensity and duration of smoking and risk. Quitting smoking reduces the risk of bladder cancer. Smoking black (air-cured) cigarettes results in a higher risk than smoking blond (flue-cured) tobacco cigarettes; results on inhalation patterns and use of filter are not consistent. Cigar and pipe smoking also increases the risk of bladder cancer; data on other tobacco products are limited. The evidence for non-transitional bladder carcinoma is limited, but consistent with an increased risk. The available evidence does not point towards a different carcinogenic effect of tobacco smoking in men and women or in whites and blacks. Data on involuntary smoke and use of smokeless tobacco products are limited, but do not suggest an increased risk of bladder cancer.