The aim of this study was to evaluate if continuous treatment with budesonide or salmeterol influences the bronchodilator response to terbutaline in children with asthma; 23 children, aged 7 to 16 years (mean = 11 years), with mild asthma were treated with inhaled budesonide 100 micrograms b.i.d. and placebo for three weeks in a randomized, double blind crossover study. These treatments were followed by treatment with inhaled salmeterol 50 micrograms b.i.d. for 3 weeks. On the last day of each period a cumulative dose-response experiment with terbutaline in the doses 50, 100, 250 and 500 micrograms (cumulative dose 900 micrograms) was performed. Lung function was measured before and 20 min after each terbutaline inhalation. Baseline pulmonary functions after budesonide treatment were significantly higher than the baseline measured after the two other treatments (p < 0.05). After budesonide treatment, the dose-response curve was shifted vertically upwards but otherwise parallel to the dose-response curve after placebo. The increase from baseline after the first cumulative dose of terbutaline was significantly lower after salmeterol treatment than after the two other treatments (p < 0.01). Maximal lung functions after 900 micrograms terbutaline also differed significantly between the three dose-response days; budesonide being significantly higher and salmeterol significantly lower than placebo (p = 0.02 and p < 0.001, respectively). It is concluded that budesonide treatment does not enhance the brochodilator response to terbutaline. Further studies are needed to assess if long-term continuous salmeterol treatment reduces the response to terbutaline.