This study evaluated the effect of inhaled aclidinium bromide on exercise endurance and in reducing resting and dynamic lung hyperinflation in patients with moderate to severe COPD. It was 9 weeks in duration, consisting of; a 2-week run-in period, 6 weeks of double-blind treatment, and a 1-week follow-up phone call. All patients meeting the eligibility criteria were randomized to one of two treatment groups: aclidinium bromide or placebo.