The exposures to total dust of a group of carbon black workers with selected circulatory, malignant, and respiratory diseases were compared with the exposures of nonaffected, matched control workers. Exposure was calculated by combining ambient air measurements (mg/m3) for each job category with the months workers had spent in each job. The cumulative total dust exposure levels of the cases were comparable to those of the controls, with the exception of men who had diseases of the circulatory system and who had experienced significantly less exposure than had the matched control workers. The results of this study indicate that exposure to carbon black in the workplace does not increase the workers' risks of circulatory, malignant, or respiratory morbidity.