Chronic gastritis is a chronic inflammation of the gastric mucosa, manifested by chronic vomiting of varying frequency. The microflora of the digestive tract, mucosal epithelium, infiltration and character of inflammatory cells and inflammatory mediators that lead to disturbances in the immunity of the gastric mucosa participate in the development of chronic inflammation. The classification of chronic gastritis is carried out according to the predominant cellular infiltrate, changes in the architecture of the mucosa and the degree and intensity of the changes. Lymphocytic - plasmacytic gastritis of unknown cause is the most common form of gastritis in dogs. Therapeutically, it responds well to antisecretory and immunosuppressive therapy and a controlled diet. Eosinophilic gastritis is often accompanied by the development of dermatological symptoms caused by dietary sensitivity. Hypertrophic and atrophic gastritis are less common in dogs. Hypertrophic gastritis is associated with breed – specific gastropathies or gastroenteropathies (brachycephalic breeds and Basenji breed). Atrophic gastritis is associated with gastric adenocarcinoma in Norwegian Lundehunds. According to current scientific knowledge, the treatment of Helicobacter pylori infection of the gastric mucosa is carried out only in dogs with digestive symptoms and histopathological findings of Helicobacter spp. in the gastric mucosa. Reflux gastritis is a common occurrence in dogs, in which a change of food is necessary along with giving more frequent meals. The diagnosis of chronic gastritis is established by endoscopic examination and biopsies of the gastric mucosa. Treatment is according to the results of histopathological findings.