Following an initial 3-week screening period qualifying patients were randomized to either tiotropium or placebo at Visit 2. Patients returned to the clinic at weeks 6 (Visit 3), 12 (Visit 4), 24 (Visit 5), 36 (Visit 6), 48 (Visit 7) and at Week 50 for the conclusion of the trial (Visit 8). The patients received treatment daily for 48 weeks (336 days).