To evaluate the efficacy and safety of clarithromycin in acute exacerbation of chronic obstructive pulmonary disease, we administered clarithromycin(250mg) twice in a day in 30 patients with acute exacerbation of chronic obstructive pulmonary disease from September to November in 1996. Twenty eight eases of 30 patients were cured(93.4%) and 2 cases(6.7%) show clinical improvement. Three cases were improved within 3 days of treatment and 24 cases were improved between 5 days and 12 days of treatment. There were no significant side effects. These results suggest that clarithromycin will be effective as a first line therapy in patients with acute exacerbation of chronic obstructive pulmonary disease.