We have to consider the exacerbation of chronic obstructive pulmonary disease(COPD) may be caused not only by infection, but also by acute exacerbation of chronic heart failure, pulmonary embolism, pneumothorax, or other cardiopulmonary complications. Because it is characteristic that the exacerbation of COPD is often recurensive, the most important thing is the administration during stable status. Approximately 40% of pathogens of the acute infectious exacerbation of COPD are Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Pseudomonas aeruginosa, Staphylococcus aureus, and Echelisia coli. Also, approximately 15% is exacerbated by atypical pathogens such as Chlamydia pneumoniae and approximately 30% is by viral infection. We should contemplate the possibility of pathogens according to the statistics, when we choose antibiotics empirically.