3. Material & methods The investigators enroll patients diagnosed with peptic ulcer, endoscopically. Helicobacter pylori is documented with Urea breath test or silver staining biopsy specimen or polymerase chain reaction of biopsy specimen. Check the 23S rRNA A2142G/A2143G point mutation by polymerase chain reaction. If there is mutation, the investigators consider as resistance to clarithromycin and choose the treatment regimen containing a proton pump inhibitor, amoxicillin, metronidazole. If there is no mutation, choose the treatment regimen containing a proton pump inhibitor, amoxicillin, clarithromycin. Verify Helicobacter pylori eradication by urea breath test. Compare eradication rate with conventional treatment,proton pump inhibitor, amoxicillin, clarithromycin.