In this study the bronchodilating effect of salbutamol (CAS 18559-94-9) after administration a single-dose (100 micrograms) from a novel multiple dose powder inhaler (MDPI; Easyhaler) and from a conventional metered dose inhaler (MDI) was compared. Forty adult asthmatic patients participated in a double-blind, randomized, cross-over, multicenter study with double-dummy technique. The study comprised two study days with a 4-h follow-up period of spirometric indices and measurements of blood pressure and heart rate. Both the powder and aerosol treatments caused a clear increase in spirometric parameters. The mean (SD) maximum forced exspiratory volume in one second (FEV1) after powder delivery was 2.82 (1.13) l and after aerosol 2.77 (1.03) l. The mean percentual change from the baseline in FEV1 was equal after both preparations. The mean area under the curve (AUC) of the absolute FEV1 values was 616 (264) and 609 (240) l x min after the powder and aerosol delivery, respectively. The treatments had no clinically significant effects on blood pressure or heart rate and were equally well tolerated. Thus the clinical effects indicate therapeutical bioequivalence of the powder and aerosol treatments. Furthermore, most patients found the handling of the MDPI device easier than or equal to that of the conventional MDI, which in all probability increase the patient compliance, which is one of the corner stones in the inhalation therapy of bronchial asthma.