The aim of this study was to compare the efficacy and safety of formoterol versus salbutamol as reliever medication in patients presenting at an emergency dept with acute asthma.A randomised, double-blind, double-dummy, parallel group study was performed in four Australian emergency treatment centres. The study included a total of 78 adult patients (mean baseline forced expiratory volume in one second (FEV1) 1.83 L; 59% predicted) with acute asthma. Based on the expected dose equivalence of formoterol Turbuhaler (R) 4.5 mu g (delivered dose) and salbutamol pressurised metered-dose inhaler 200 mu g (metered dose), patients received a total of formoterol Turbuhaler (R) 36 mu g (delivered) or salbutamol pressurised metered-dose inhaler with spacer 1,600 mu g (metered), divided into two equal doses at 0 and 30 min. FEV1, peak expiratory flow and systemic beta(2)-agonist effects were monitored for 4 h. The primary variable was FEV1 % pred at 45 min.At 45 min, mean increases in FEV1 expressed in % pred were 6.6% and 9.3%, respectively, with a small adjusted mean difference in favour of salbutamol (3.0%, 95% confidence interval -2.0-8.0). Transient increases in systemic beta(2)-agonist effects occurred predominantly with salbutamol, although no significant treatment differences were observed. Eight patients discontinued due to adverse events.In this study of patients presenting at emergency depts with acute asthma, formoterol Turbuhaler (R) 36 mu g was well tolerated and, as rescue therapy, had an efficacy that was not different from that of salbutamol pressurised metered-dose inhaler with spacer 1,600 mu g in the number of patients studied.