BACKGROUND: Pleural abnormality is the the most common respiratory change caused by asbestos dust inhalation and also develp other asbestos related disease after cessation of asbestos exposure. So we conducted epidemiologic study to investigate if the pleural abnormality is associated with pulmonary function change and what factors are influenced on pulmonary function impairement. METHODS: Two hundred and twenty two asbestos workers from 9 industries using asbestos in Korea were selected to measure the concentration of sectional asbestos fiber. Questionnaire, chest X-ray, PFT were also performed. All the data were analyzed by student t-test and chi-square test using SAS. Regressional analysis was performed to evaluate importent factors, for example smoking, exposure concentration, period and the existence of pleural thickening, affecting to the change of pulmonary function. RESULTS: 1) All nine industries except two, airborn asbestos fiber concentration was less than an average permissible concentration. PFT was performed on 222 workers and the percentage of male was 88.3%, their mean age was 41+/-9 years old, and the duration of asbestos exposure was 10.6+/-7.8 yrs. 2) The chest X-ray showed normal(89.19%), pulmonary Tb(inactive)(2.7%), pleral thickening (7.66%), suspected reticulonodular shadow(0.9%). 3) The mean values of height, smoking status, concentration of asbestos fiberwere not different between the subjects with pleural thickening and others, but age, cumulative pack-years, the dura-tion of asbestos exposure were higher in subjects with pleural thickening. 4) All the PFT indices were lower in the subjects with pleural thickening than in the subjects without pleural thickening. 5) Simple regression analysis showed there was a significant correlation between FEF75 which is sensitive in small airway obstruction and cumulative smoking pack-years, the duration of asbestos exposure and the concentration of asbestos fiber. 6) Multiple regression analysis showed all the pulmonary function indices were decreased as the increase of cumulative smoking pack-years and especially in the indices those are sensitive in small airway obstruction. Pleural thickening was associated with reduction in FVC,FEV1, PEFR and FEF25. CONCLUSION: The more concentration of asbestos fiber and the more duration of asbestos exposure, the greater reduction in FEF50,FEF75. Therefore PFT was important in the evaluation of early detection for small airway obstuction. Furthermore pleural thickening without asbesto-related parenchymal lung disease is associated with reduction in pulmonary function.