This issue of Clinics in Chest Medicine, guest-edited by Dr. Gerard Criner and Dr. Bartolome Celli, is focused on Chronic Obstructive Pulmonary Disease. Topics discussed in this issue include but are not limited to: COPD Pathogenesis; Epidemiology of COPD; Host, Gender, and Early Life Factors as Risks for COPD; Alpha One Antitrypsin Deficiency; Lung Function Testing; Assessing Symptom Burden; Chest Imaging in the Diagnosis and Assessment of the Patient with COPD; Biomarkers in the Diagnosis and Assessment of COPD; Asthma/COPD Overlap; Multimorbidity in the Patient with COPD; Definition Causes, Pathogenesis, and Consequences of Exacerbations; Treatment of Acute Exacerbations; Prevention of Exacerbations; Bronchodilators; Benefits and Risks of Inhaled Corticosteroids in COPD; Systemic Medications; Smoking Cessation/Vaccinations; Pulmonary Rehabilitation; Oxygen Therapy/Noninvasive Ventilation; and Interventional and Surgical Therapies for COPD.