The health status of sheet metal workers (SIC-1711) was investigated in 50 sheet metal firms in California. Toxic exposure and mortality data was obtained from union records, interviews with workers, and environmental studies during sheet metal operations. The total population included 1,301 workers. Proportionate mortality was studied in 364 deaths that occurred in two cohorts of sheet metal workers from 1950 to 1970 and an additional 423 deaths identified from claims to a pension plan. In both sexes there was an excess of deaths due to malignant neoplasms; the excess was attributable to malignant tumors of the respiratory tract. There were also excesses in deaths due to accidents other than motor vehicle accidents, cirrhosis of the liver, and suicide. Standardized mortality ratios (SMR) were calculated for two cohorts of 1,670 and 1,031 men observed for 28,438 and 12,422 persons years, respectively. Analysis of 307 deaths in the first and 83 deaths in the second cohort showed that the overall SMR was better than expected in both groups, but there was an apparent excess of lung cancer. The authors suggest that the greatest factor contributing to the lung cancer risk was exposure to asbestos (1332214).