Duodenal ulcer is associated with such genetic characteristics as blood group O and secretor status. Since Helicobacter pylori has been proved to be an important factor in the pathogenesis of duodenal ulcer, we wanted to study whether the frequency of H. pylori antibodies would vary in individuals with different blood group antigens. Antibodies against H. pylori were determined in 271 blood donors. Acid glycine extract from an H. pylori strain was used as antigen in enzyme immunoassay. Our results suggested no significant association of increased level of H. pylori antibodies with ABO blood group and secretor status, which implies that H. pylori infection is not associated with the ABO group and secretor status. Thus H. pylori and blood group antigens seem to be independently linked to duodenal ulcer.