We have demonstrated recently that 1 year of regular inhaled budesonide use can produce substantial improvements in airway responsiveness accompanied by significant improvements in clinical asthma severity. The present study was designed to evaluate whether these improvements are maintained when the dose of budesonide is reduced. At the end of the original study, 28 subjects with asthma, who had been in the active-treatment arm of the study were randomized either to continue taking the dose of budesonide taken in the original study or to have the dose reduced. Airway responsiveness to methacholine, bronchodilator requirements, symptoms, and spirometry were assessed after 6 weeks and 3 months. During the 3 months, no subject experienced an asthma exacerbation, and there was no evidence of change in airway responsiveness in subjects who had their steroids reduced (provocative concentration causing a 20% drop in FEV1; initial, 2.03 mg/ml; final, 1.91 mg/ml), and this change was not different from change in subjects maintained with a higher dose (initial, 3.02 mg/ml; final, 3.12 mg/ml) (p = 0.39). Similarly, there was no evidence of any change in bronchodilator requirements (p = 0.89). However, after 3 months of reduced steroid use, there was a small decline in spirometry (FEV1 percent predicted: initial, 84.4%; final, 81.5%), and this change was significantly different from change in subjects in whom steroids were not reduced (initial, 90.2%; final, 90.2%) (p = 0.002). At 3 months, symptoms (predominantly sputum production) were also beginning to redevelop in the reduced budesonide group (p = 0.056).(ABSTRACT TRUNCATED AT 250 WORDS)