The role of airway inflammation in the pathogenesis of asthma in childhood is uncertain. In the present study, 27 atopic and nonatopic children aged 7-9 yrs who had > or = 5 episodes of wheeze and symptoms of exercise-induced asthma (EIA) in the previous 12 months, performed a methacholine challenge and exercise test on separate days at monthly intervals. The subjects had not received oral or inhaled corticosteroids for 12 months prior to the study. The dose-response relationship to inhaled methacholine was expressed as the cumulative dose provoking a 20% decrease in forced expiratory volume in one second (PD20). Forced expiratory volume in one second (FEV1) and peak expiratory flow (PEF) were measured prior to the exercise test and at 0, 3, 5, 10, 15 and 20 min following maximal exercise. Following the first methacholine challenge and exercise test, the children were randomized in a double-blind manner to receive inhaled beclomethasone dipropionate (BDP) 200 micrograms b.i.d. or a placebo b.i.d. from a Diskhaler for 3 months. All children were asymptomatic at the time of testing, and there was no significant change in the baseline FEV1 of any subject prior to either challenge throughout the study period. When compared to placebo, the bronchial responsiveness to exercise and methacholine was significantly attenuated in the children who had received inhaled BDP for at least 1 month. There was no relationship between the bronchial responsiveness to methacholine and exercise. There was no significant difference in the bronchial responsiveness to either stimulus in the atopic and nonatopic children. The results of this study suggest that immunoglobulin E (IgE)- and non-IgE-mediated airway inflammation are important in exercise- and methacholine-induced bronchoconstriction in children with recurrent wheeze, although it is probable that different mechanisms are responsible.