Acute and chronic changes of ventilatory capacities and thernprevalences of respiratory symptoms were studied in 233 (117rnmales and 116 females) nonsmoking factory workers exposed torncotton, tobacco and cement dusts. Two hundred and thirty six (125rnmales and 111 females) workers who were nonsmokers and had nornexposure to occupational dusts were taken as non-exposedrnsubjects. An attempt was made to see values of ventilatoryrnindices in relation to dust concentration and duration ofrnexposure. Comparison was also made between dust concentrationsrnrecorded in this study and standards recommended by ACGIH andrnWHO. Prevalences of respiratory symptoms (chronic cough, chronicrnbronchitis, and bronchial asthma) were found to be higher in allrndust-exposed groups than they were in the non-exposed subjects.rnAll respiratory symptoms considered in the present study werernfound in cement and cotton workers much more frequently than inrnthe non-exposed sUbjects. Only chronic cough was found to be morernfrequent among tobacco workers than among the non-exposedrnsUbjects. significant reductions of FVC, FEV1, MMFR and PEFR rn values over the workshift were recorded among cotton and tobacco rnworkers. Acute reductions in cement workers were recorded only in rnFVC and PEFR. Significantly reduced mean values of FEV1%, FEF rn, MMFR in both sexes of exposed subjects and FEV1 and PEFR in male rn Exposed subjects were recorded. After matching of exposed subjects, fromrneach factory, with the non-exposed subjects according to theirrnage and height, significantly reduced mean values of FEV1%, FEF,rnMMFR in both sexes of cotton workers and PEFR in male cottonrnworkers were recorded. Mean values of FEVl% and MMFR in cementrnworkers, FEVl in female tobacco workers and PEFR, MV and MVV inrnmale tobacco workers were found to be significantly lower than inrnthe non-exposed sUbjects. Substantial number of workers werernfound to have lower values of ventilatory capacities than theirrnpredicted values by more than two standard errors of estimate.rnPredicted values of ventilatory indices were calculated for bothrnsexes by means of multiple linear regression equations, developedrnon the basis of data obtained in the non-exposed subjects.rnMean percentages of predicted lung function values inrnworkers exposed to relatively high dust concentration were foundrnto be lower than the values observed in those exposed to lowerrnconcentration, but significant differences (in FEVl %) werernobserved only in cement workers. strong negative correlations (rS-O.30) rnwere recorded between duration of exposure and FVC, FEVl , FEV1% and rn MMFR values in male exposed subjects. Negative correlations were also rn observed among females, but the relationships were not as strong as that ofrnmales. When compared with standards of ACGIH and WHO, the dustrnconcentrations in cement and yarn factories were found to bernhigh.