OBJECTIVE To investigate the distribution and antibiotic resistance of nonfermenting gram-negative bacilli isolated from lower respiratory tract infection patients from 2003 to 2007 for rational antimicrobial therapy in practice.METHODS The data of distribution and antibiotic resistance of nonfermenting gram-negative bacilli isolated from sputum samples of lower respiratory tract infection in our hospital from 2003 to 2007 were retrospectively analysed.RESULTS The most predominant nonfermenting gram-negative bacilli isolates were Pseudomonas aeruginosa,Acinetobacter baumannii,Acinetobacter lwoffii and Stenotrophomonas maltophilia.From 2003 to 2007,the resistance rates of these isolates to 15 antibiotics increased,especially P.aeruginosa to ceftazidime.The resistance changed from 30.2% in 2003 to 55.4% in 2005,54.8% in 2006,and reduced to 41.5% in 2007.The resistance to gentamicin,imipenem,netilmicin,ticarcillin and tobramycin varied in the similar way.The resistance of A.baumannii to imipenem increased from 21.1% to 59.7% within the five years.The resistance rate of A.lwoffi was still relatively low.S.maltophilis isolates were highly multi-resistant to antimicrobial agents tested with a rate ranging from 61.9%-100.0% except ceftazidime,ticarcillin and trimethoprim-sulfamethoxazole.CONCLUSIONS P.aeruginosa,A.baumanii and S.maltophilia are the main nonfermentive pathogens of lower respiratory tract infections and not susceptive to many antibiotics.The tendency of susceptibility and distribution changes of those bacteria should be considered in practice for proper antimicrobial therapy.