Various modes of pneumoconiosis supervision in Japan were assessed in a national survey which evaluated copies of results from 43,483 worker pneumoconiosis examinations. The examination copies indicated age, sex, mode of supervision, category of chest radiograph, complications, pulmonary dysfunction, history of dust work, symptoms, and signs. The four modes of supervision for workers engaged in dust work included: mode-1, for persons considered unaffected by pneumoconiosis; mode-2, which required reduction of exposure to dust; mode-3, which required change of work; and mode-4, for persons whose radiographic appearances corresponded to category-4 or those whose radiographic appearances corresponded to category-1, category-2, category-3, or category-4 and who had considerable pulmonary dysfunction due to pneumoconiosis requiring medical treatment. Mode-4 of supervision was applicable to 1.3% of all subjects. Pulmonary dysfunction, mainly attributed to depression of percent vital capacity or forced expiratory volume in one second, was often the basis for deciding on this mode. Secondary bronchitis and pulmonary tuberculosis accounted for more than 90% of diseases causing complications.