The presentation of chronic obstructive pulmonary disease (COPD) usually is insidious, and many patients are undiagnosed until the disease is far advanced. Therefore, the early use of spirometry is recommended for anyone who is suspected to have COPD. In the early stages of the disease, the patient is only mildly symptomatic (cough and sputum production). As COPD becomes more advanced, functional impairment in the form of chronic dyspnea occurs and acute exacerbations of symptoms become more frequent, contributing to overall morbidity and mortality. The single most important known causative factor of COPD is cigarette smoking. Smoking cessation remains, therefore, the mainstay of COPD therapy. In patients with advanced disease, symptomatic treatment with the regular use of either short- or long-acting sympathomimetic and/or anticholinergic bronchodilators, singly or in combination, should be added to smoking cessation and influenza and pneumococcal vaccination therapies. An inhaled corticosteroid, either alone or more commonly in combination with a long-acting bronchodilator, can further reduce exacerbations and improve the health status of these patients. Furthermore, patients with severe COPD, particularly those who are debilitated, should be considered for pulmonary rehabilitation because these programs have been proven useful in maintaining, or in some cases improving, health status for these patients. Finally, correction of resting arterial hypoxemia with oxygen therapy for more than 15 h/d prolongs survival of COPD patients for those with a resting PaO2 lower than 55 to 60 mm Hg.