The incidence of bladder cancer continues to increase, with an estimated 53,000 new cases diagnosed in the United States in 1996-90% of which are transitional cell carcinomas. The male-to-female ratio is 3:1. A number of etiological factors are associated with the development of bladder cancer, but in industrialized countries, cigarette smoking is the most important. Specific chemicals have also been identified as causing bladder cancer, as have a number of occupational exposures to less well-defined specific agents. Treatment with cytostatic drugs, especially cyclophosphamide, is associated with increased risk of bladder cancer, as is treatment with radiotherapy for uterine cancer. In developing countries, especially in the Middle East and parts of Africa, infections with members of the genus Schistosoma are responsible for a high incidence of bladder cancer-75% of which are squamous cell carcinomas. Arsenic has been indicated as a bladder carcinogen in Argentina, Chile, and Taiwan. The reason for the high incidence of urinary tract cancer in individuals suffering from Balkan nephropathy has yet to be determined. A careful history of patients with bladder cancer is an important and useful process in helping to identify causal factor and, in more than one-half the cases, a known relationship is found. Bladder cancer is a potentially preventable disease, with a significant morbidity and mortality in many parts of the world.