Diabetes mellitus is one of the most serious problems of the clinical medicine. This is determined by the fact that it is followed by multisystemic affects, as well as complications on the side of other organs and systems, among which a special place is occupied by gastroesophageal reflux disease. As for the combination and mutual influence of diabetes mellitus and gastroesophageal reflux disease, this issue has not been studied yet, the data of modern literature are not complete and quite contradictory.The aim of the study: to investigate the state of the factors of aggression and protection of the oesophageal mucosa in patients with diabetes mellitus type II with concomitant gastroesophageal reflux disease without associated pathology.Method. There were two groups of patients under observation. The first group included 45 patients with diabetes mellitus type II with concomitant gastroesophageal reflux disease (26 men and 19 women). The second group included 38 patients with gastroesophageal reflux disease without associated pathology – 20 men and 18 women. By sex, age, body weight, Helicobacter pylori infection, smoking and alcohol consumption, both groups were comparable. The surveillance program included determining the compensation ratio of carbohydrate metabolism and the state of the factor. The antioxidant protection factor was assessed by the level of catalase activity in the blood serum, as well as by the diameter of the celiac trunk and the blood flow velocity in it. Statistical processing of the obtained data was carried out with the aid of the program WINDOWS STATISTIKA 6.0. For all types of analysis, differences were considered statistically significant with p<0.05.Results. During the study, we found that in patients with diabetes mellitus type II with concomitant gastroesophageal reflux disease, as well as in patients with gastroesophageal reflux disease without associated pathology, the level of pH-metry was reduced, but with varying measures of confidence. At the same time, we found that patients with GERD without associated pathology had a decrease in the blood flow velocity in the celiac trunk. Concurrently, we ascertained that the decrease in the blood flow velocity in patients of both groups reduced the diameter of the celiac trunk. Conclusions. In patients with diabetes mellitus type II, concomitant gastroesophageal reflux disease has a subtle clinical presentation that is affected by a significant decline in mucosal sealing protection factors. In patients with GERD without associated pathology, typical clinical manifestations, accompanied by inflammation, acid regurgitation and dyspepsia, are more vivid.