The primary objective of this trial was to establish non-inferiority of lung function response to two doses [25 μg (1 capsule) and 50 μg (2 capsules of 25 μg)] salmeterol, administered as the xinafoate salt, in an inhalation powder delivered from hard polyethylene (PE) capsules via the HandiHaler® 2 compared to Serevent® Diskus® (salmeterol 50 μg, administered as the xinafoate salt) following single dose inhalation in patients with COPD. A hard capsule with half the strength (12.5 μg) was included to investigate a dose ordering effect.