The study aimed to estimate the relative dose potency of salbutamol inhaled via Turbuhaler and Diskhaler. The 24 adult patients participating had chronic reversible airway obstruction. The study was of a double-blind, double-dummy, crossover, randomized design. Five doses of salbutamol Turbuhaler, 50, 50, 100, 200, and 400 microg, were given on one study day at intervals of 30 min. On another study day, five doses of salbutamol Diskhaler, 200, 200, 400, 800, and 1600 microg, were given with the same interval. The treatment days were separated by a washout period of at least 24 h. The inhalation technique was standardized and supervised. Efficacy variables were recorded before and after each study dose. The primary efficacy variable was forced expiratory volume in 1 s (FEV1). When parallel and linear cumulative dose-response curves were statistically compared on a logarithmic scale, the dose potency of salbutamol Turbuhaler vs salbutamol Diskhaler was 1.99 (95% confidence interval 1.52-2.54). This study indicates that only half the dose of salbutamol is required via Turbuhaler as via Diskhaler for the same bronchodilating effect.