The present study examined the bronchodilator and safety profiles of single-dose indacaterol in intermittent or persistent asthma. In the present double-blind crossover study, 42 patients were randomised to receive single doses of indacaterol (50, 100, 200 and 400 microg) or placebo via a hydrofluoroalkane pressurised metered-dose inhaler. The primary efficacy comparisons were the per cent changes in forced expiratory volume in one second (FEV(1 )) between indacaterol and placebo 30 min and 21 h post-dose. All doses resulted in prolonged bronchodilation, with indacaterol 200 and 400 microg meeting pre-specified efficacy criteria. The mean percentage increases in FEV(1) from placebo with indacaterol 200 and 400 microg were 7.6 and 14.9%, respectively, at 30 min, and 7.5 and 10.4%, respectively, at 21 h post-dose. At these doses, changes in mean FEV(1) relative to placebo were statistically significant from 5 min to 25 h, inclusive. At 5 min, the geometric least squares mean values for FEV(1) were 3.08 and 3.22 L for the 200 and 400 microg doses, respectively, compared with 2.99 L for placebo. At 24 h after dosing, the baseline-adjusted geometric least square mean FEV(1) was 3.13, 3.11, 3.24 and 3.30 L for indacaterol 50, 100, 200 and 400 microg, respectively, and 2.98 L for placebo. All treatments were well tolerated. Once-daily indacaterol at doses of 200 and 400 microg provided sustained 24-h bronchodilation, with a rapid onset and a good tolerability and safety profile.