Three hundred thirty-four healthy male non-smokers and 300 healthy male smokers of the age range 20-60 years were investigated for their spirometric lung functions by the method and technique recommended by American Thoracic Society. It was found that FVC, FEV1, FEV1%, FEF 200-1,200, FEF 25-75%, FEF 75-85%, MVV, and PEFR were significantly lower in smokers. When the subjects were blocked into several half decades these differences persisted. These functions deteriorated with age both in smokers and non-smokers, but in the former group the functions were reduced to a greater extent. Significant negative correlation was obtained between lung functions and smoking histories. Separate multiple regression equations were developed separately for non-smokers and smokers. The sensitivity of the tests was determined. The FEF 25-75% and FEV1 were found to be most sensitive in detecting early airway obstruction. When comparison of lung function was made among American, European, Jordanian, Negro, and Pakistani subjects, it was found that the former three groups are superior to the remaining. Negroes and Pakistanis are comparable to Indians in respect to their lung function. These differences in these functions between the nations of developed countries and the underdeveloped or developing countries might be attributable to the differences in their life-style, physical activity status, nutritional status, environmental condition, and race and ethnicity. The spirometric functions of Indians in the Eastern region of India are comparable to North-West Indians and superior to Southern Indians.