Retrograde duodenogastroscopy solves the problem of postoperative evaluation of the gastric bypass patient. The stomach may be bypassed to treat morbid obesity, but it no longer need be inaccessible. Endoscopic gastritis is rare in the proximal gastric pouch but common in the distal gastric segment and may be related to the presence of bile. Although the gastric mucosa is histologically normal in half of the gastric bypass patients, acute and chronic gastritis, regenerative changes, and intestinal metaplasia may develop in either or both segments. The causes and implications of these endoscopic and histologic findings are unknown.