Urologic cancers include malignancies of the genital and the urinary organs of men, and the urinary organs of women. For men in the United States, urologic cancers account for about 25% of all new cases of cancer and about 15% of cancer deaths. For women, cancers of the urinary organs account for 4% of all new cases of cancer and 3% of cancer deaths. Of urologic cancers, bladder cancer has been the most intensively studied epidemiologically. Cigarette smoking is the most important known preventable cause of the disease. Occupational exposures continue to come under suspicion. It appears that neither coffee drinking nor use of artificial sweeteners are important risk factors. Current questions in the etiology of prostate cancer concern its relationships to benign prostatic hypertrophy, to components of the diet and to hormone metabolism. Little is known of the etiology of kidney cancer other than probable associations of the disease with cigarette smoking and exposure to asbestos. Testicular cancer is associated with undescended testis and possibly other urogenital anomalies. The relationships of testicular cancer to pesticide exposure, in utero estrogen exposure, and infection are current research issues.