The objective of this study is to evaluate the efficacy and safety of 12 weeks treatment with tiotro pium HandiHaler® 18 mcg daily compared to Combivent® MDI CFC Inhalation Aerosol 2 actuations qid in COPD patients currently prescribed Combivent® MDI.

Inclusion Criteria:

• Diagnosis of COPD
• Age: >= 40 years
• Current or ex-smoker with a >= 10 pack-year smoking history
• Use of Combivent® MDI for >= 1 month prior to Visit 1 Spirometric criteria (determined at study visits):
• Post-bronchodilator FEV1 <= 70% (Visit 1)
• Pre-bronchodilator FEV1 <= 65% of predicted and FEV1/FVC <= 70% (Visit 2)

Exclusion Criteria:

• Clinical history of asthma
• History of thoracotomy with pulmonary resection
• History of CF, alpha 1 antitrypsin deficiency or interstitial lung disease
• Daytime use of oxygen therapy for > 1 hour per day or if unable to abstain from using oxygen during PFTs
• Any respiratory tract infection or COPD exacerbation in 6 weeks prior to Visit 1
• Recent history 6 months or less of MI
• Unstable or life-threatening cardiac arrhythmias
• Hospitalization for CHF during past year
• Malignancy for which patient is receiving chemo or radiation therapy
• Pregnant or nursing women
• Known hypersensitivity to ipratropium or carrier substances, including related food products such as soybean, peanuts, or lactose
• Use of SPIRIVA® 3 months prior to Visit 1
• Symptomatic of prostatic hypertrophy or bladder neck obstruction
• Known narrow- angle glaucoma
• Participating in a pulmonary rehab program within 4 weeks of Visit 1