Large-scale production of aromatic amines that serve as intermediates in the aniline dye industry began in this country during World War I. In the United States, the first known occupationally induced aromatic amine cancers of the bladder were observed at a dye factory in 1931. Additional cases of benzidine-related bladder cancer was subsequently reported at this same facility and at numerous other dye works in this country and throughout the world. In 1974, the Occupational Safety and Health Administration promulgated a standard to control the production and use of benzidine in the workplace. Although hazards associated with benzidine exposure have been reduced, a carcinogenic risk due to benzidine-based dye exposure is now apparent. In addition, several dyes produced from o-tolidine and o-dianisidine, carcinogenic compounds structurally related to benzidine, have demonstrated metabolism to their respective parent compounds. The history of occupational bladder cancer in the United States is traced and measures taken by the Occupational Safety and Health Administration to reduce exposure to this hazard are described.