An epidemiologic study in an engineering company was prompted by the observation of three cases of cancer; it revealed several more cancers among women who wrapped bearing rings covered with antirust oil, ie, 12 cases vs 3.9 expected. The 12 tumors were situated in different organs, including the uterus, ovaries, breast, thyroid, brain, colon, and bladder. No known carcinogenic substance was found that could explain the increased incidence of cancer. If the increased incidence is not a random phenomenon, N-phenyl-1naphthylamine or its nitroso derivative is likely to be the causative agent.