Abstract: Objective: To analyze the pathogenic bacterial distribution and drug-resistance before and after chemotherapy in advanced lung cancer patients with respiratory infections. Methods: Sputum specimens were collected from advanced lung cancer patients with respiratory infections between January 2005 and May 2007. Bacterial culture and antibiotic sensitivity tests were performed. Results: A total of 309 specimens were collected with 145 taken before chemotherapy and 164 tak-en after chemotherapy (≥4 cycles). The most commonly detected strains were C.albicans, A.cloacae, B.catarrhalis, A.bau-manii and K. pneumoniae. No significant difference was found in bacterial spectrum between the pre-chemotherapy speci-mens and the post-chemotherapy specimens(P>0.05). The following antibiotics were effective before and after chemothera-py: Fluconazole, Itraconazole, Cefoperazone/sulbactam and Ceftazidime, with no changes in sensitivity(P>0.05). Resistance to Ampicillin, Imipenem, Aztreonam, Cefaclor and Levofloxacin increased after chemotherapy (P<0.05). The resistance to Cefoxitin and Cefazolin decreased after chemotherapy(P<0.05). Conclusion: The species of the predominant strains of mi-crobes present in respiratory infections in advanced lung cancer patients were different from those found in other types of patients. Gram-negative bacteria and fungi dominate the spectrum, and the fungal infection rate is higher in advanced lung cancer patients than in other patients. Chemotherapy has no major influence on the effect of antibiotics, but several antibiotics, most of which are biobasic-cephalosporins and penicillins, have decreased efficacy in patients with multicycle chemotherapy.