Following an initial screening visit, patients will enter a 2-week baseline period. Patients who successfully complete this phase will be randomized into the double-blind portion of the study in which they will receive tiotropium once daily (morning) or Atrovent four times daily. Pulmonary function testing will be conducted just prior to the start of therapy at Visit 2 (i.e. randomization visit after completion of the 2-week run-in period) and at 120 minutes post-dosing. Pulmonary function testing will be repeated at the same time intervals at the end of therapy.