Using a randomized double blind study design, the bronchodilating effect of 200 micrograms inhaled oxitropium bromide (OB) was compared with 200 micrograms inhaled fenoterol (F) after an interval of 20 min, in 20 asthmatic children aged 12.7 years (range: 4.9-15.1 years), suffering from mild bronchoconstriction (mean forced expiratory volume during ls: 73.4%, range: 51%-85%). Both drugs induced a comparable degree of bronchodilatation and no significant differences were found between the OB group and the F group, suggesting equipotency for both drugs after a 20 min interval, at the 200 micrograms dose level. Furthermore, a significant improvement of lung function parameters was detected in both groups after subsequent administration of 400 micrograms F, indicating that inhalation of 200 micrograms of OB or F results in submaximal bronchodilation in asthmatic children suffering from mild bronchoconstriction.