Thirteen children with asthma were treated with cumulative doses of terbutaline delivered as a pressurized aerosol and from a new multidose powder inhaler (Turbuhaler) in a randomized cross-over dose-response study. The cumulative dose of terbutaline was 2 mg on each study day. All children used a correct aerosol inhalation technique. At no time was there any difference in forced expiratory volume in 1 s (FEV1), forced midexpiratory flow, forced vital capacity, peak expiratory flow rate, or percent increase in these parameters between the two inhalers. The mean total increases in FEV1 after 2 mg terbutaline were 60% (aerosol) and 62% (Turbuhaler); 90% of these increases were measured after a cumulative dose of 0.5 mg terbutaline. One milligram of terbutaline inhaled from a Nebuhaler at the end of each study day did not result in additional increase of pulmonary functions, indicating that maximal bronchodilation had been achieved with both inhalers. After a cumulative dose of 2 mg terbutaline from the aerosol seven children complained of tremor and one of restlessness. No side effects were reported when the Turbuhaler was used (P less than 0.02). 1989; 7:00-00.