Indacaterol is a novel, inhaled, once-daily, ultra-long-acting β(2)-agonist bronchodilator recently approved in Europe for the treatment of chronic obstructive pulmonary disease (COPD). The aim of the present study was to investigate the efficacy and safety of indacaterol compared with placebo and the twice-daily β(2)-agonist, salmeterol, as an active control. Patients with moderate-to-severe COPD were randomised to 6 months double-blind treatment with indacaterol (150 μg once daily), salmeterol (50 μg twice daily) or placebo. The primary efficacy end-point was trough (24 h post-dose) forced expiratory volume in 1 s (FEV(1)) after 12 weeks. 1,002 patients were randomised and 838 (84%) completed the study. Indacaterol increased trough FEV(1) at week 12 by 170 mL over placebo (p<0.001) and by 60 mL over salmeterol (p<0.001). Both active treatments improved health status (St George's Respiratory Questionnaire) and dyspnoea (transition dyspnoea index) compared with placebo, with differences between them favouring indacaterol. Safety profiles were similar across the treatment groups, and both indacaterol and salmeterol were well tolerated. Once-daily treatment with 150 μg indacaterol had a significant and clinically relevant bronchodilator effect over 24 h post-dose and improved health status and dyspnoea to a greater extent than twice-daily 50 μg salmeterol. Indacaterol should prove a useful additional treatment for patients with COPD.