The majority of researchers discover associations between H. pylori (Hp) and serum IL-8 production with the stage of chronic inflammation. Data on IL-8 levels in chronic gastritis (CG) and a gastroduodenal ulcer (GDU) are insufficient, and often controversial. All patients with chronic active gastritis (CAG) and GDU were divided into 4 subgroups: patients with GDU and found Hp infection according to common methods (GDU+Hp), patients with GDU and no documented Hp infection (GDU), patients with CAG and found Hp infection according to common methods (CAG+Hp), and patients with CAG with no documented Hp infection (CAG). The highest serum IL-8 levels were seen in patients with GDU+Hp, whereas the lowest ones were observed in patients with CAG. Men have the lowest IL-8 levels in the CAG+Hp subgroup as compared with other subgroups. The IL-8 values were significantly different from higher values in women. The rate of fecal Oantigen of H. pylori LPS found using the coagglutination test is 86%. The highest levels of O-antigen of H. pylori LPS were detected in the CAG subgroup. In patients with GDU+Hp, the levels of O-antigen of H. pylori LPS were significantly higher as compared with the GDU subgroup. So patients with GDU, especially those with GDU+Hp, and with CAG, have active IL-8 production. Coagglutination to detect O-antigen of H. pylori LPS in feces used along with common methods increases the probability to confirm that the patients (especially those with chronic gastritis) are infected with this microbe.