An epidemiological study was carried out in three textile mills of Ahmedabad. A total of 214 cotton dust exposed and 184 control subjects were examined for pulmonary function tests. Pulmonary function tests included forced vital capacity and forced expiratory volume in one second. The pulmonary function tests were carried out before starting the shift and after 7 hours of exposure on a vitalograph spirometer. The study shows that among the cotton dust exposed workers byssinotics behave distinctly and show the maximum acute and chronic changes in pulmonary functions. It seems that the effect of cotton dust exposure on the byssinotic subjects is more predominant than the effect of smoking.