The incidence rate of bladder cancer in the Barcelona area of Spain is almost identical to that of the U.S. Cigarette smoking has been identified as the most significant risk factor for bladder cancer, followed by occupational exposures to chemicals such as aromatic amines and their derivatives, diesel exhaust, oil mist, pesticides, and polynuclear aromatic hydrocarbons. A variety of non-occupational exposures have been suggested as potential risk factors as well, including smoking black vs. blond tobacco, dietary factors, certain medications and medical conditions, chlorination by-products in drinking water, and fluid intake. Various genetic polymorphisms also appear to affect bladder cancer risk. Research is needed to further explore hypotheses generated by previous etiologic studies of bladder cancer. An ongoing study of bladder cancer survival by the institut Municpal d'Investibacio Medica in Spain provides an excellent opportunity for NCI to perform such research. NCI will build upon the ongoing study by funding an interdisciplinary case-control component to evaluate bladder cancer risk in relation to various external factors (e.g., occupational and environmental exposure) and host factors (e.g., genetic susceptibility marker, and early effect markers). This hospital-based case-control study will involve personal interviews using a state-of-the-art, computer-assisted technique, and collection of blood and toenail samples from participants.