Helicobacter pylori (H. pylori) is a Gram-negative, curved bacillus known since 1983. It is supposed to play role in the pathogenesis of certain gastroduodenic diseases, e.g. non-ulcer dyspepsia (NUD), chronic inflammation, ulcers, etc. Serum samples of 70 patients who were examined for stomach complaints with gastroscopy and those of 22 healthy persons were analysed. The purpose of the study was to evaluate anti-H. pylori IgG, IgM and IgA antibodies using ELISA method. Whether the antibodies can be detected or not, 8 possible variations exist, each of them denoting certain state of infection. These states are not always going parallel with the macroscopic pictures revealed by gastroscopy, but there are some obvious congruences. Results show that serologic examination cannot replace gastroscopy but on the other hand in follow-up tests and examinations as well as in understanding the aetiology of different gastroduodenal diseases it can play an important role.