Efficacy and safety of umeclidinium administered in a dry power inhaler were evaluated in moderate-to-very-severe chronic obstructive pulmonary disease patients. This was a randomised, placebo-controlled study assessing once-daily umeclidinium 62.5 and 125 μg over 12 weeks. The primary end-point was change from baseline in trough forced expiratory volume in 1 s (FEV1) on day 85. Secondary end-points were 0-6-h weighted mean and serial forced expiratory volume in 1 s. Other end-points were transitional dyspnoea index, health outcomes (St George's Respiratory Questionnaire), pharmacokinetics and safety. 246 patients were enrolled; 168 completed the study. On day 85, umeclidinium 62.5 and 125 μg significantly improved least squares mean change from baseline in trough FEV1 (127 and 152 mL, respectively; p<0.001) compared with placebo. On day 84, umeclidinium 62.5 and 125 μg significantly improved least squares mean change from baseline in 0-6-h weighted mean (166 and 191 mL, respectively; p<0.001) and serial FEV1 at each time point (p≤0.003). Significant improvements in least squares mean transitional dyspnoea index focal score for UMEC 125 mg(1.3 units; p,0.05) and change from baseline St George's Respiratory Questionnaire total score for both UMEC doses (-7.9 and -10.87 units, for UMEC 62.5 mg and 125 mg, respectively; both p,0.001) were noted compared with placebo at week 12 [DOSAGE ERROR CORRECTED].The incidence of adverse events was low and similar across treatments. Umeclidinium 62.5 and 125 μg significantly improved lung function, dyspnoea and health status compared with placebo, and were well tolerated in chronic obstructive pulmonary disease patients over 12 weeks.