Exacerbations of chronic obstructive pulmonary disease (COPD) are a source of substantial morbidity. In this randomized, controlled trial involving patients with moderately severe COPD, daily treatment with azithromycin for 1 year was associated with fewer exacerbations. Acute exacerbations of chronic obstructive pulmonary disease (COPD) result in frequent visits to physicians' offices and emergency rooms and numerous hospitalizations and days lost from work; they also account for a substantial percentage of the cost of treating COPD. 1 – 5 Patients who have acute exacerbations of COPD, as compared with patients with COPD who do not have acute exacerbations, have an increased risk of death, a more rapid decline in lung function, and reduced quality of life. 6 – 11 Although inhaled glucocorticoids, long-acting beta 2 -agonists, and long-acting muscarinic antagonists reduce the frequency of acute exacerbations of COPD, 12 – 24 patients receiving . . .