AIM: The eradication rate of Helicobacter pylori(H pylorl)shows variation among countries and regimens of treatment.We aimed to study the eradication rates of different regimens in our region and some factors affecting the rate of eradication.METHODS: One hundred and sixty- four H pylori positive patients (68 males, 96 females; mean age: 48±12 years)with duodenal or gastric ulcer without a smoking history were included in the study. The patients were divided into three groups according to the treatment regimens. Omeprazole 20 mg, clarithromycin 500 mg, amoxicillin 1 g were given twice daily for 1 week (Group I) and 2 weeks (Group II).Patients in Group III Received bismuth subsitrate 300 mg,tetracyline 500 mg and metronidazole 500 mg four times daily in addition to Omeprazole 20 mg twice daily. Two biopsies each before and after treatment were obtained from antrum and corpus, and histopathologically evaluated.Eradication was assumed to be successful if no H pylorus was detected from four biopsy specimens taken after treatment. The effects of factors like age, sex, H pylori density on antrum and corpus before treatment, the total H pylori density, and the inflammation scores on the rate of H pylori eradication were evaluated.RESULTS: The overall eradication rate was 42%. The rates in groups II and III were statistically higher than that in group I (P＜0.05). The rates of eradication were 24.5%,40.7% and 61.5% in groups I, II and III, respectively. The eradication rate was negatively related to either corpus H pylori density or total H pylori density (P＜0.05). The median age was older in the group in which the eradication failed in comparison to that with successful eradication (55 yr vs 39 yr, P＜0.001). No correlation between sex and H pylori eradication was found.CONCLUSION: Our rates of eradication were significantly lower when compared to those reported in literature. We believe that advanced age and high H pylori density are negative predictive factors for the rate of Hpylori eradication.