In 2005, Australian scientists Robin Warren and Barry Marshall were awarded the Nobel Prize in physiology and medicine for the discovery of the bacterium Helicobacter pylori and for the study of its role in the development of gastritis and peptic ulcer. H. pylori is a gram-negative, microaerophilic bacterium that colonizes the gastric mucosa (GM) and that is associated with atrophic gastritis, peptic ulcer disease (PUD), gastric adenocarcinoma and extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). Epidemiological studies confirm that more than 50% of people worldwide are currently infected with this microorganism. Virtually all infected individuals develop H. pylori-associated chronic gastritis that is, however, latent in the majority of them. Over time, only 20% of the infected individuals develop serious diseases: peptic ulcer disease, GM atrophy, and 1-3% of patients are at high risk for gastric adenocarcinoma. Based on the data of epidemiological studies of the role of the microorganism in the processes of carcinogenesis in the stomach, the World Health Organization' International Agency for Research on Cancer (IARC) recognized H. pylori as a Class 1 carcinogen in 1995. The new European guidelines for the management of H. pylori infection, presented in September 2011 at the regular 24th Meeting of the International Working Group on the study of H. pylori and related bacteria in chronic inflammatory processes in the gastrointestinal tract and in gastric cancer, cover not only new approaches to the therapy of H. pylori infection, but also its current diagnostic methods. These methods are classified into invasive and noninvasive; the former involve an endoscopic study of GM biopsy specimens and the latter include various immunological studies that determine serum antibodies or fecal bacterial antigen, as well as a urease breath test. The endoscopic study is one of the most important techniques to evaluate GM in patients with H. pylori-associated pathology. The application of new optical diagnostic technologies, such as narrow-band imaging magnifying endoscopy, allows differentiation of the smallest abnormal structural changes in the GM, which cannot be detected by routine endoscopy or that cannot be biopsied for the diagnosis of precancerous alterations and early gastric cancer.Chronic gastritis (CG) is the most common disease that occupies one of the first places in the pattern of gastrointestinal tract diseases. It occurs in 50-80% of the population in our country, as estimated by different authors [1, 2]. The disclosure of Н. pylori has been revolutionary and made incredible progress in gastroenterology. This allows contemporary internists to gain an insight into the fact that the bacterium H. pylori is an important participant in the development of abnormalities, such as acute gastritis and CG, PUD, gastric cancer and MALT lymphoma [3] and to devise new, more effective diagnostic methods for Н. pylori infection and etiopathogenetic principles in the treatment and prevention of Н. pylori-associated diseases.