Background: Helicobacter pylori infection occurs worldwide, but the prevalence varies greatly among countries and among population groups studied. People with blood group O have been noted to be more susceptible to H. pylori infection. Objectives: To determine the magnitude of H. pylori infection in adult patients with and without dyspeptic symptoms attending Felege Hiwot Hospital, Bahir Dar, North West Ethiopia. We also prospectively examined the relationship between H. pylori infection and ABO blood groups in those subjects to clarify the possible association. Methods: A case-control study was conducted between dyspeptic (n=100) and non-dyspeptic patients (n=100) for the presence of H. pylori infection between mid November 2002 and March 2003 by using serology. Results: Of the total 200 subjects, 128 (64%) were males and 72 (36%) females with mean age of 32.7, range 15-75, years. Of these, 112 (56%) and 66 (33%) were found positive and negative for H. pylori infection, respectively, by EIA. Borderline values were measured in 22/200 (11%). H. pylori infection was detected in 124/200 (62%) of study subjects by immunoblot. The most prevalent blood group was type O (43%), followed by A (23.5%), B (22.5%) and AB (11%). In comparison of the subjects with blood group O and the other blood groups, no statistical significance could be identified in the seroprevalence of H. pylori ( p>0.05). Conclusion:The overall seroprevalence of H. pylori infection in Bahir Dar in this study was between 63% and 70% in dyspeptic patents and 49% and 54% in non-dyspeptic patients by EIA and IB, respectively. There were no statistically significant differences in the frequency of H. pylori seroprevalence between dyspeptic and non-dyspeptic patients. There was no statistically significant association between H. pylori infection and sex, age and ABO blood groups. Thus, further investigations along this line are recommended. [Ethiop.J.Health Dev. 2005;19(1):55-59]