In a two-day, randomised, double-blind, double-dummy, cross-over multicenter study, the bronchodilating effect of 100 micrograms of salbutamol (CAS 18559-94-9) inhaled from a new metered dose powder inhaler (MDPI; Taifun) was compared with that of an identical dose of salbutamol inhaled from a conventional pressurised metered dose inhaler connected to a spacer (pMDI + S). Thirty-six non-smoking, adult asthmatic outpatients with a baseline forced expiratory volume in 1 s (FEV1) between 35 and 70% of the predicted value participated in the study. After inhalation of the study medication pulmonary function, FEV1 and airway resistance (R(aw)), blood pressure (BP), and heart rate (HR) were measured up to 6 h. Area under the FEV1 vs. time curve (AUCFEV1) was used as the primary efficacy parameter, and the 90% confidence intervals (CI) were used to judge clinical equivalence. Other efficacy parameters were used in supportive analyses as secondary parameters. Both treatments produced a clear improvement in pulmonary function. The mean +/- SD AUCFEV1 were 893 +/- 281 and 889 +/- 2761.min after MDPI and pMDI + S, respectively. The 90% CI for the relative efficacy of the MDPI is from 98 to 103% of that of the pMDI + S. Also the other efficacy parameters gave similar results without significant differences: the mean +/- SD values of percent increase in FEV1 were 47.2 +/- 19.3 and 44.7 +/- 20.8, the maximum absolute value of FEV1 were 2.87 +/- 0.77 and 2.86 +/- 0.77, the maximum percent decrease in R(aw) 53.2 +/- 20.5 and 55.0 +/- 19.1, and the minimum absolute value of R(aw) 0.27 +/- 0.11 and 0.30 +/- 0.12 kPa.s.l-1 for the MDPI and pMDI + S, respectively. The salbutamol doses had no significant effect on BP or HR, and were equally well tolerated. Furthermore, 57.5% of the patients preferred the MDPI, 35% the pMDI + S, and 7.5% considered that there was no difference between the devices. In conclusion, this study demonstrates that the new MDPI is as effective and safe a device as a conventional pMDI connected to a spacer in administering inhaled salbutamol for asthmatic patients. Further, most patients considered the MDPI easier to handle, and preferred it over the pMDI + S.