A quantitative assessment of the lung cancer risk associated with occupational cadmium (7440439) (Cd) exposure was performed. Data were taken from a NIOSH study of mortality in all white males employed at a smelter for at least 6 months between 1 January 1940 and 31 December 1969. The analysis was also restricted to include only those workers who were hired on or after 1 January 1926 to reduce possible confounding by arsenic (7440382), since the facility had operated as an arsenic smelter from 1918 to 1925. A Cd exposure matrix was constructed using company air monitoring data and employment records. Vital status of the cohort was determined as of 31 December 1984. Causes of death were determined from which standardized mortality ratios (SMRs) were computed using a NIOSH life table program for comparing the number of deaths in the cohort with that of the United States population. Separate analyses were performed for Hispanic and nonHispanic workers to minimize confounding by smoking since Hispanics have been reported to experience lower lung cancer rates. Dose response relationships between Cd exposure and lung cancer mortality were examined using various functional forms of the Poisson and Cox proportionate hazards models. A total of 606 workers contributing 16,898 person years of exposure met the criteria for inclusion in the cohort. Mortality from lung cancer was significantly elevated in the entire cohort, SMR 149. Lung cancer mortality was significantly increased among nonHispanic workers, but less than expected in Hispanic workers, SMRs 211 and 49, respectively. Lung cancer mortality was greatest in workers with the highest cumulative Cd exposures, more than 2,921 milligram days per cubic meter, and those with more than 20 years exposure, SMRs 272 and 161, respectively. Applying an exponential model to the risk assessment indicated that the lifetime excess lung cancer risk for exposure to Cd fumes at the current OSHA standard, 100 micrograms per cubic meter, would amount to 49.9 to 110.9 lung cancer deaths per 1,000 workers for a 45 year exposure.