Introduction: Bile reflux gastritis is due to an excessive reflux of duodenal contents into the stomach. The increasedenterogastric reflux may provide the basis for increased mucosal injury. In clinical practice the symptoms of bile reflux gastritis are nonspecific than the other gastritis. Only endoscopy and biopsy can confirm the diagnosis. Observation demonstrates that, in practice there is tendency to increase the bile reflux gastritis. However, in Mongolia there are much less research and studies in this area. Goal: Evaluate the endoscopical and histological changes caused by duodenal reflux on the gastricmucosa Materials and Methods: We included in our study 70 patients with bile reflux gastritis admitted in Second General Hospital in Ulaanbaatar. In all cases we performed an upper gastrointestinal endoscopy and at least 4 biopsyspecimens were done from antral mucosa and the histological features were scored in accordance with the Sydney system. Results: The average age of the patients with bile reflux gastritis was 61.64±9, 69 years. Reflux gastritis was noted to 15 males and 55 females. Gastroduodenal reflux after chlocystoectomic surgery was noted in 46 cases (65.71%), and biliarytract disease was noted in 16 cases (22.85%). The average time interval from original operation tothe discovery of the bile reflux gastritis was 9.22 years after chlocystoectomic surgery. The commonest endoscopic alterations were: erythema of the gastric mucosa in 41 cases (58.57%),gastric antral atrophy in 20 cases (28.57%), gastric diffuse atrophy in 27 cases (38.57%), thepresence of bile into the stomach in 70 cases (100%), erosions in 3 cases (4.28%), gastric ulcer in2 cases (2.85%), intestinal metaplasia in 10 cases (14.28%).The histologic alterations observed from tissues collected during endoscopic examination were chronic super facial gastritis in 19 cases (27.14%), chronic atrophic gastritis in 51 cases (72.85%),an intestinal metaplasia in 32 cases (14.28%), gastric erosions and ulcer in 4 cases (5.71%),dysplasia in 1case (1.42%), Helicobacter pylori infection in 14 cases (20%). Conclusions The most frequent risk factors for bile reflux gastritis were chlocystoectomic surgery and biliary tract disease. Histological findings of patients with bile reflux gastritis revealed gastric cancer precursor lesions, therefore follow-up endoscopic examinations and early treatment of bile reflux are essential.