Occupational urinary tract cancers were discussed. After the skin and lung, the bladder is the most common target organ of known occupational carcinogens. The number of bladder cancer cases attributed to occupational factors has been estimated to be as high as 20 percent; however, other estimates suggest 10 to 20 percent in males and 5 percent in females. Cancer of the kidney was reviewed. Occupational kidney cancer is a relatively recently identified disease and the occurrence and etiology is poorly understood at present. Approximately 15 percent of kidney neoplasms are in the renal pelvis and appear to be caused by the same carcinogens as bladder cancer, while the remaining 85 percent are in the parenchyma and have an apparently different etiology. There is considerable international variation in the incidence of kidney tumors, and it occurs in males at twice the frequency of females. The percentage of kidney cancers attributed to occupational factors has not been reported, since there is too little data for useful estimates. For occupational kidney cancer, the prime challenge in terms of research is to identify the extent of occurrence and etiology. The Registry of Toxic Effects of Chemical Substances published by NIOSH indicates that 174 substances have been found to cause kidney tumors in animals or humans. The relevancy of findings of kidney cancers in experimental animals to humans is questionable. Bladder cancer was reviewed. Bladder cancer has been regarded as an occupational disease since 1895. Many aromatic amines have been described as potent bladder carcinogens. The National Occupational Hazard Survey of 1972 to 1974 estimated that there are approximately 13,000,000 workers in occupations or industries with established or probable associations with bladder cancer. Of these, 150,000 workers in the United States were identified in the National Occupational Hazard Survey as potentially exposed to benzidine based dyes, and 6000 workers have been identified as being at high risk of bladder cancer due exposure to aromatic amines. The authors conclude that there is a pressing need for evaluating and implementing the most promising and effective means of bladder cancer control for such high risk workers.