The main purpose of this study is to determine the feasibility and effects of a 6-month tai chi exercise program as compared to a 6-month group walking program and standard care for patients with COPD that have recently completed a pulmonary rehabilitation program.

Inclusion Criteria:

1. COPD defined as FEV1 (Forced expiratory volume in 1 second)/FVC (Forced vital capacity) <0.70 or chest CT evidence of emphysema
2. Age > 40 years
3. Any severity of COPD as defined by GOLD (Global Obstructive Lung Disease) stages 1, 2,3, or 4
4. Completion of standard pulmonary rehabilitation of at least 8 weeks duration within 24 weeks prior to study entry* *Defined as attending 65% of the program's sessions with a minimum of 10 sessions

Exclusion Criteria:

1. COPD exacerbation requiring steroids, antibiotics, ED visit or hospitalization within the past 2 weeks unless physician deems subject at baseline
2. Hypoxemia on walk test (O2 sat < 85% on oxygen)
3. Inability to ambulate due to vascular or other neuromuscular conditions that would preclude a walk test
4. Clinical signs of unstable cardiovascular disease (ie. chest pain on walk test)
5. Severe cognitive dysfunction (documented Mini-Mental Status Exam ≤ 24)
6. Non-English speaking
7. Current regular practice of tai chi
8. Current diagnosis of lung cancer or treated for lung cancer within the past 5 years
9. Unstable/untreated mental health issue that precludes informed consent or otherwise affects ability to participate in the intervention