Mucosal alterations after vertical banded gastroplasty-Roux-en-Y gastric bypass has not been clearly evaluated, since the excluded stomach is not easily reached by conventional endoscopy. The new technique of enteroscopy, a double-balloon method, enables endoscopic evaluation of the excluded stomach. Aim: To analyze the histological findings and the presence of Helicobacter pylori (H. pylori) in the excluded stomach. Methods: Forty consecutive patients who underwent Roux-en-Y gastric bypass longer than 36 months were selected for double-balloon enteroscopy. The excluded stomach was reached in 35/40 patients (87.5%). All H. pylori positive patients were treated before surgery. Morphological alterations were analyzed through hematoxilin and eosin and the presence of H. pylori was confirmed with Giemsa staining. Results: Thirty patients (85.7%) were female and the mean age was 43.4 years-old. The mean post-operative time was 77.6 months (range 36 - 110 months). Eight cases (8/35, 22.8%) presented endoscopically normal bypassed stomach. According to Sydney classification, 4/35 (11.4%) patients had body or antrum gastritis, including three atrophic and one erythematous. Twenty-three patients (23/35, 65.7%) had pangastritis, including nine erythematous, nine flat erosive and five atrophic. Two patients 2/35 (5.7%) also had suspicious areas of intestinal metaplasia. Histologically, all patients had chronic gastritis in the bypassed stomach, with pangastritis in 33/35 (94.3%). Five cases (5/35, 14.3%) presented atrophy and four of them also had intestinal metaplasia. Mild gastritis were detected in 23/35 (65.7%) and moderate gastritis in 12 out 35 (34.3%). No severe gastritis was found. H. pylori was detected in 7/35 (20%) of the excluded stomach, and was positive in the antrum in all of them, and also positive in the body in four patients. Severity of gastritis of the excluded stomach was associated to the presence of H. pylori, p=0.02. Moreover, H. pylori was positive in the gastric stump (functional pouch) in 12/35 (34.3%). All positive H. pylori patients in the excluded stomach were also positive in the gastric stump, p=0.0005. Conclusions: 1. H. pylori is still present in the excluded stomach after Roux-en-Y gastric bypass and might be considered for treatment; 2. Histological findings indicated high prevalence of atrophy and intestinal metaplasia in this selected population; 3. Long-term endoscopic follow-up with biopsies is advised.