This paper presents the efficacy and cost of therapy with azithromycin for the treatment of patients with acute exacerbation of chronic obstructive pulmonary disease (COPD). Two subgroups were investigated: out-patients and hospitalized patients--20 in each group (17 women and 23 men). Azithromycin 500 mg was administered sequentially once daily. A complete physical examination including temperature, respiratory rate, cough, production and characteristics of sputum so as general aspects of quality of life assessed by COPD exacerbation questionnaire was made in hospitalized patients on a daily base and in a day 10-14 after the end of therapy. Out-patients were assessed in day 1, 3-5 days after the start of study drug treatment and 10-14 days after the end of therapy. Pulmonary function tests were assessed three times during the whole study course. The results of the study suggest similar duration of therapy with azithromycin in both study subgroups, whereas in out-patients decrease and regression of symptoms were statistically significantly quicker with tendency approximately the same in both study subgroups. The cost of therapy with azithromycin was similar in both subgroups but the complete cost of COPD exacerbation treatment was significantly lower in out-patients in comparison to hospitalized patients group (473.71 PLN and 2587.87 respectively).