Classifications of chronic gastritis and neoplastic gastric diseases, developed in recent years (1996 Houston update of 1990 Sidney classification system, 2002 New Orlean classification of atrophic gastritis according to recommendations of International Group for Atrophy Studies; 1998 Padova classification of gastric displasia, and 1998 Vienna classification of gastrointestinal neoplasia) allow to statandardize international research and perform more objective diagnostics of pathological changes in the gastric mucosa. Studies carried out in recent years have established that morphological manifestations of chronic gastritis caused by Helicobacter pylori infection can be reduced after its eradication. Longterm treatment with proton pump inhibitors have been demonstrated not to cause atrophic changes in the gastric mucosa when undertaken after successful eradicational therapy. It has been established that corporal gastritis intensifies in patients treated with proton pump inhibitors. The studies show that measurement of serum levels of Helicobacter pylori antibodies, gastrine, pepsinogen I and II can be used in non-invasive serologic diagnostics of atrophic gastritis. Achievements in diagnostics and treatment of chronic gastritis create the necessary prerequisites for the development of gastric cancer preventing measures.