AIM:To investigate the resistance rate of Helicobacterpylori(Hpylori)to clarithromycin,metronidazole,amoxicillin andtetracycline to guide clinical practice,and to study themechanism of Hpyloriresistant to clarithromycin.METHODS:Thirty Hpylori strains were isolated from themucosa of peptic ulcer,gastric tumor and chronic gastritispatients,then the minimal inhibitory concentration(MIC)toclarithromycin,metronidazole,amoxicillin and tetracyclinewas evaluated by E-test method.The sequence analysis ofPCR fragments was conducted in 23S rRNA gene of Hpyloriresistant to darithromycin to get the resistance mechanismof the bacteria.RESULTS:Among 30 Hpyloristrains,7 cases were resistantto clarithromycin,12 to metronidazole,2 to tetracycline andno strain was found to be resistant to amoxicillin.Theresistance rates were 23.3%,40%,6.7% and 0%,respectively.Three new mutation points were found to berelated to the clarithromycin resistance in Hpyloriisolates,which were G2224A,C2245T and T2289C.CONCLUSION:In northeast China,Hpylorishows highresistance to metronidazole,while sensitive to amoxicillin.The mechanism of resistance to clarithromycin may be relatedto the mutation of G2224A,C2245T and T2289C in the 23SrRNA gene. To investigate the resistance rate of Helicobacter pylori (Hpylori) to clarithromycin, metronidazole, amoxicillin and tetracycline to guide clinical practice, and to study the themechanism of Hpyloriresistant to clarithromycin. METHODS: Thirty Hpylori strains were isolated from themucosa of peptic ulcer, gastric tumor and chronic gastritis patients, then the minimal inhibitory concentration (MIC) toclarithromycin, metronidazole, amoxicillin and tetracycline is evaluated by E-test method. The sequence analysis of PCR fragments was conducted in 23S rRNA gene of Hpyloriresistant to darithromycin to get the resistance mechanism of the bacteria. 30 Hpyloristrains, 7 cases were resistantto clarithromycin, 12 to metronidazole, 2 to tetracycline and no strain was found to be resistant to amoxicillin .resistance rates were 23.3%, 40%, 6.7% and 0% respectively.Three new mutation points were found to berelated to the clarithromycin resistance in Hpylori isolates, which were G2224A, C2245T and T2289C.CONCLUSIO N: In northeast China, Hpylorishows high resistance to metronidazole, while sensitive to amoxicillin. The mechanism of resistance to clarithromycin may be related to the mutation of G2224A, C2245T and T2289C in the 23S rRNA gene.