The effect of indoor air pollution due to domestic cooking with biomass fuel and liquefied petroleum gas (LPG) on the course of bronchial asthma was examined in one hundred non-smoking female asthmatics. The parameters for evaluation were symptoms, emergency visits, and drug requirements. The patients also measured peak expiratory flow rate (PEFR) at home five times daily over a period of one week and the levels of carboxyhaemoglobin (COHb) were estimated randomly during clinic visits. The COHb levels (%) were 4.1 +/- 0.9 and 3.5 +/- 0.6 in the two groups with 22-30% of the subjects reporting increased symptoms during cooking. The number of emergency admissions and the daily requirement of steroids were comparable in both the groups. The PEFR values were lower than the predicted values in both the groups at all times. Further, the readings after exposure to cooking fuels were lower than those before cooking in both the groups (p < 0.01) and these values were similar to those observed during early morning records at 6 AM, which were the lowest. It was concluded that exposure to biomass fuel and LPG affect pulmonary function (PEFR) in asthmatics and both types of fuels affect the airway function and symptoms of bronchial asthma in a similar manner.