Five hundred fifty-four workers, 84% of whom are chronic cigarette smokers, have been examined during the past year with emphasis on the role of sputum cytopathology in the early detection and diagnosis of lung cancer. Of the 554, 232 (42%) have shown squamous metaplasia, 44 (8%), mild to moderate atypias, 18 (3.2%), severe atypias, and two (0.4%), squamous carcinoma. Both of the carcinomas were in x-ray negative, cytopathology-positive elderly cigarette smokers. Ferruginous bodies have been found in the sputa of 187 (33%) workers. Ferruginous bodies in the sputum do not appear to be a marker for severe atypias; rather, their presence correlates best with duration and extent of industrial exposure to asbestos.