Morphological changes in gastric mucosa were studied, optimal terms of bariatric operations performance after intragastric balloon (IGB) insertion were determined. Before the IGB insertion in 10 (35.7%) patients, in accordance to histological investigations, the changes in gastric mucosa were not revealed, and in 18 (64.3%) - chronic gastritis was established. In accordance to endoscopic investigation results, immediately after the IGB removal in 23 (82.1%) patients a pronounced erythematous gastropathy was noted, and in 5 (17.9%) - erosive gastropathy. While investigating the gastric mucosa biopsies in all the patients a prominent inflammatory changes were revealed, including significant edema, pronounced lymphocytic infiltration. In accordance to esophagogastroduodenoscopy data on the 14-th day of endoscopic monitoring in 6 (21.4%) patients pathological changes of gastric mucosa were not revealed, in 22 (78.6 %) - erythematous gastropathy was noted, and in accordance to histological investigation - chronic gastritis. Persistence of IGB in gastric cavity during 6 mo caused a morphological changes in gastric mucosa - a significant inflammation, what was confirmed by endoscopic and histological investigations data. The gastric mucosa structure normalization was observed in 14 days after the IGB removal, that's why a radical bariatric intervention is recommended to perform not earlier the term established.