Twenty-five per cent of the authors' total upper endoscopy experience since 1974 has been in patients who have had upper gastrointestinal tract surgery. The observations from 617 examinations in 400 of these patients is reviewed. Pain or nausea and vomiting was a common presenting symptom. Multiple complaints were frequent. Gastritis was the most common endoscopic finding present in 127 patients (32%). Biopsy yielded an 89% histologic confirmation of the endoscopic perception. Coexisting mucosal pathology was common, with 39% of the patients having two or more abnormalities. X-ray in 190 patients had only a 30% accuracy rate and a frequent occurrence of false negatives (46%). Bezoars and intraluminal sutures were seen commonly and endoscopy provided a therapeutic choice for enzyme injection of the bezoar and removal of the sutures. Endoscopy provided a method of evaluation of our highly selective vagotomy technique; 96% of our patients with ulceration at the time of surgery were healed by endoscopy and 93% had active antral-pyloric function.