The primary purpose of this trial was to evaluate whether the effect of inhaled tiotropium (Spiriva®) on the change in trough FEV1, compared to placebo, was affected by smoking status. The primary endpoint was defined as the change in trough FEV1 after 48 weeks of treatment. The primary analysis was performed in a sequential fashion; firstly, the analysis was performed for all patients and if a positive signal was seen in this group, the analysis was then performed for both the smoking and ex-smoking groups separately. Patients were defined as smokers or ex-smokers at the screening visit.