Short-acting β₂-agonists are currently recommended for symptom relief in asthma and the treatment of mild, acute exacerbations in COPD. However, formoterol has as fast an onset of action as salbutamol with the additional benefit of longer-lasting bronchodilation (approximately 12h). Furthermore, systemic side effects observed with formoterol are of a similar duration but less pronounced than with short-acting β₂-agonists. In this double-blind, randomized, cross-over study, 20 adult patients with reversible chronic airway obstruction (intrinsic asthma or COPD) inhaled single doses of formoterol 9μg or salbutamol 100μg (group A) or formoterol 18μg or salbutamol 200μg (group B). FEV₁ was measured prior to and 5, 10, 15, 20, 25 and 30min following inhalation of study drug. No significant differences in FEV₁ values were observed between group A (P=0.704) or group B (P=0.270) at baseline, or at 5 (Group A: P=0.340; Group B: P=0.559) and 15min (Group A: P=0.526; Group B: P=0.818) post dose. No adverse events were reported during the study. Formoterol Turbuhaler has as rapid an onset of action as salbutamol pMDI when given at the recommended doses.