In this study we compared the development of anti-H. pylori humoral response in adults and children. Two antigens: H. pylori acid glycine extract (GE) and recombinant cagA were used for ELISA and Western blot. Anti-GE IgG were detected in all and anti-cagA IgG in about 50% of H. pylori infected adults and children. The prevalence of anti-GE and anti-cagA IgG in the sera from H. pylori-uninfected children with gastritis/gastroduodenitis was lower than in the sera from healthy adult blood donors. Serum IgA were demonstrated for 71% of H. pylori-infected adults and for a smaller proportion (about 30%) of uninfected adult patients or normal subjects. Such antibodies were detected neither for infected nor for uninfected children. There was an evident difference between the proteins of H. pylori glycine extract recognized by antibodies present in the sera from H. pylori-infected children and adults. The antigen of molecular weight over 107 kDa was recognized exclusively by the sera from 30% of H. pylori-infected adults. The 80-107 kDa bands were recognized more frequently by the sera from adults than from children. In contrast, sera from infected children more frequently than sera from infected adults reacted with the bands of 14 kDa, 19 kDa and 26 kDa. The H. pylori antigens recognized by IgG, produced by infected children and adult patients, should be taken into consideration in the developing of tests for serodiagnosis of H. pylori infection.