Acute exacerbations, most of which are due to lower respiratory tract infections, cause great morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD) and most of these are due to lower respiratory tract infections. The aim of this study was to determine the causative organism and the effects of azithromycin, ampicillin sulbactam (sultamicillin), ciprofloxacin and cefaclor monohydrate therapy in COPD. One hundred and six patients with COPD in acute exacerbation were randomized into four groups for empiric antibiotic treatment following lung function tests and sputum examination. The most common strains isolated from sputum were Haemophilus influenzae (30.8%), Streptoccocus pneumoniae (12%) and Moraxella catarrhalis (7.7%). Azithromycin, sultamicillin, ciprofloxacin and cefaclor monohydrate were found to be effective in treating COPD exacerbations.