Lung Function test results can be influenced by race, socioeconomic status, and physical fitness. The choice of the most appropriate predictive equations should be based upon these considerations as well as age, sex, and body size. About 70% of Korean males smoke, and non-smokers can be a selective group in Korea. In this study, lung function test results of 683 healthy Korean male workers were analyzed to get the predictive equations of Forced Vital Capacity(FVC), Forced Expiratory Volume in 1 second(FEV(1)), and FEV(1)/FVC (FEV(1)%). The age of studied workers ranged from 18to 60, and most of those finished high school or less. Healthy smokers without any respiratory symptoms or disease history were included in the study, while the effect of smoking on the test results were examined in the analysis. FVC, FEV(1), and FEV(1)% were regressed against age, height, weight and smoking status or smoking amount. Age and height explained FVC and FVC(1) most efficiently and the contribution of other variables were not significant. Whereas, smoking was significantly associated with a decrease in FEV(1)% even among healthy un-symptomatic workers. For FEV(1)%, age, height, and smoking amount were significant variables, constituting the most efficient prediction model. The lower limit of normal for percent predicted values was calculated from lower 95 percentile as well as 95% confidence interval. When the results of this study was compared to those from studies of white Caucasians, the predicted FVC and FEV(1) were lower for the given age and height but the differences were less than 10%. The slopes of regression equation for height and age were, however, not significantly different when the social backgrounds of the studied subjects were similar.