Lung function parameters, forced vital capacity (FVC), forced expiratory volume in 1st s (FEV1), peak expiratory flow rate (PEFR), were measured in 3,318 nonsmoking Indian women using four different types of cooking fuels (biomass, liquified petroleum gas, kerosene and mixed). Biomass fuel users had FVC values less than 75% predicted (73.42 +/- 0.90; mean +/- SE) whereas in other groups it was more than 75% of predicted, though less than 80% of the predicted values. However, FEV1, FEV1/FVC (%) and PEFR were within normal limits in all the four groups. The absolute values of all the three parameters of lung functions were the lowest in the biomass and mixed fuel users. A negative correlation was observed between these parameters and the duration of cooking and exposure index. Thus the present study showed that, lung function, particularly FVC, is affected by indoor air pollution due to domestic cooking more so with biomass fuel. Better housing and use of smokeless devices for cooking might be helpful to avoid this effect on lung. This ventilatory impairment seems to be more of the restrictive (parenchymal) type, since obstruction could be ruled out. A longitudinal study is needed to demonstrate whether or not these changes are variable, reversible or progressing to fibrosis.