A study of lung cancer mortality in steelworkers exposed to acid mists was conducted. This was a followup to an earlier survey of 1165 workers in pickling operations at three steel factories. The workers were exposed to sulfuric-acid (7664439) aerosols at mean concentrations of 0.2mg/m3, below the OSHA standard of 1mg/m3. The vital status of the cohort was determined at the end of 1986. Complete smoking histories of the subjects were determined in early 1986. Standardized mortality ratios (SMRs) were calculated using the United States general population as the reference. The lung cancer SMRs were adjusted for smoking using an equation that estimated the effects of differences in smoking habits between the cohort and referent population on lung cancer mortality. The overall SMR for lung cancer unadjusted for smoking was 1.56. The lung cancer SMRs for subjects with less than 5 years, 5 to 20 years, and more than 20 years' exposure were 1.26, 1.73, and 1.68, respectively. SMRs for other causes of death were close to those of the referent population. After adjusting for smoking, the lung cancer SMR for the entire cohort was 1.36 and the SMR for subjects having more than 20 years exposure was 1.50. The authors suggest that an elevated risk of lung cancer exists in steelworkers having relatively low exposures to acid mists, after adjusting for smoking.