ObjectiveTo investigate drug resistance of Mycobacterium tuberculosis (M. tuberculosis) isolated from inpatients with pulmonary tuberculosis in Shenyang Chest Hospital in recent 4 years.MethodsRetrospective analysis of drug susceptibility test of M. tuberculosis to isoniazid(INH), streptomycin(SM), ethambutol (EB) and rifampicin (RFP) was conducted, M. tuberculosis were isolated from new cases and retreated pulmonary tuberculosis patients with positive sputum culture in Shenyang Chest Hospital from January 1, 2003 to December 31, 2006. ResultsThe total drugresistant rate of M. tuberculosis was 39.11% (79/202), multidrugresistant rate was 10.89%(22/202). The initial drugresistant rate and acquired drugresistant rate was 35.11% and 46.48% respectively. The acquired multidrugresistant rate was 16.90%,which was obviously higher than that of initial multidrugresistant rate of 7.63%（χ2=4.08，P=0.049）. In 2004, the acquired multidrugresistant rate (36.36%) was obviously higher than that of initial multidrugresistant rate (5.66%)（χ2=5.95，P=0.02）. However in 2006, the two rates were the same(13.51%).The retreated patients showed a higher drug resistance to INH (47.89%), SM (46.48%) and RFP (36.62%). Multidrugresistant rate of retreated patients was 35.21%, single drugresistant rate and multidrugresistant rate of initial patients were both 16.03%.ConclusionThe results showed that the drug resistance and multidrug resistance of pulmonary tuberculosis are still serious, especially the initial drug resistance and multidrug resistance. So effective control of drug resistant tuberculosis is critical task currently.