context: the prevalence of obesity has been increasing in modern society. roux-en-y gastric bypass is a bariatric surgery that involves the exclusion of significant part of the stomach. atrophy, intestinal metaplasia and gastric cancer have been associated with infection by helicobacter pylori. objectives: to evaluate the presence of endoscopy findings and histological changes in morbid obese patients for the presence of inflammatory cells, inflammatory activity, lymphoid hyperplasia, h. pylori infection, atrophy and intestinal metaplasia in the gastric mucosa. methods: upper digestive endoscopy and gastric histopathological were studied in 126 obese patients in the preoperative evaluation for bariatric surgery. results: upper digestive endoscopy abnormalities were diagnosed in 73/126 (57.9%) patients. in three patients (2.4%) the upper gastrointestinal endoscopy diagnosed gastric ulcer and one patient (0.8%) had duodenal ulcer. the histopathological from gastric biopsies of these obese patients showed 65.1% of mucosa inflammation, inflammatory activity in 50.0%, infection by h. pylori in 53.2%, lymphoid hyperplasia in 50.0% and atrophy and/or intestinal metaplasia in 16.7%. conclusions: in present study, with routine preoperative upper gastrointestinal endoscopy and histopathological examination, were detected 57.9% patients with endoscopy abnormalities, high prevalence of infection by h. pylori (53%) and 16.7% of gastric atrophy and/or intestinal metaplasia.