Abstract One hundred fifteen adult patients with asthma participated in this open-label, randomized, parallel-group study that compared the acceptability, clinical efficacy, and tolerability of salbutamol inhalation aerosol and powder in the treatment of asthma. There were no significant differences between groups in terms of demographic variables. Before the study the patients had used inhaled steroids at least for 6 months and had shown an improvements in forced expiratory volume in 1 second (FEV 1) or in peak expiratory flow rate (PEFR) of more than 15% after the inhalation of 200 μg of salbutamol. The treatment period was 12 weeks and was preceded by a 2-week run-in period. The medications were delivered from a metered dose inhaler (MDI) and from a new multidose powder inhaler (MDPI). During the study, home PEFR was measured daily in the mornings and in the evenings. In the mornings PEFR was measured both before and 15 minutes after the inhalation of 200 μg of salbutamol. FEV 1 and forced vital capacity (FVC) were measured after the run-in period and after 4 and 12 weeks of treatment. FEV 1 and FVC were measured immediately before and 15 and 30 minutes after the inhalation of 200 μg of salbutamol. Asthma symptom scores, adverse events, and the use of rescue medication were recorded daily. Patients' preference of the inhalers (acceptability) was evaluated during the study after 4 weeks of treatment. No significant differences were found between the treatments in any of the efficacy variables measured. Of the 77 patients allocated to use the new MDPI, 72 gave their opinion about the inhalers: 34 patients (47%) rated MDPI easier to use than the MDI; 28 (39%) did not find any differences in handling between the two devices; and 10 (14%) felt the MDPI was more difficult to use than the MDI. We conclude that the new MDPI is clinically equivalent to the MDI in the long-term treatment of asthma, and the patients found it easy to use.