Background Bacteria-induced respiratory infection has been long considered to be the major cause of acute exacerbation of chronic obstructive pulmonary disease (AECOPD).Therefore,a clear picture about the distribution and drug-resistance of pathogenic bacteria in the lower airways should be helpful for treatment of the disease.So far,data on this topic among Chinese are lacking.Methods A surveillance study was performed in consecutive patients with AECOPD at five areas in China between October 2006 and April 2008.The sputum from these patients was cultured and isolated for bacteria.Agar dilution method was used to determine the minimal inhibitory concentrations (MICs) of levofloxacin and other 15 antibiotics against these strains.Results Three hundred and fifty-nine pathogenic bacterial strains were isolated among 884 patients with AECOPD.The predominant bacteria were Pseudomonas aeruginosa (21.7％),Klebsiella pneumoniae (12.3％),Haemophilus influenzae (14.2％) and Streptococcus pneumoniae (11.7％),followed by Haemophilus parainfluenzae (9.5％),Acinetobacter baumannii (7.8％),Moraxella catarrhalis (6.4％) and Escherichia coli (3.6％).The majority of bacterial pathogens isolated in this study were susceptible to fluoroquinolones,ceftazidime,cefepime and imipenem.Conclusions Gram-negative bacilli are the leading pathogens in patients with AECOPD in China.Haemophilus parainfluenzae may be one of the most important pathogens in AECOPD.This study provides evidence for local surveillance of AECOPD pathogens and appropriate choice of antimicrobials in China.