Patients who had undergone resection for gastric or duodenal ulcer 10-13, 21-22 or 31-32 years previously were offered endoscopic follow-up examination. Of the 272 surviving patients, 145 (53%) attended. No gastric stump carcinoma was found. Histologic studies showed atrophic gastritis in 79% and intestinal metaplasia in the gastric mucosa in 72% of the patients, but no definite dysplastic changes. The changes appeared soon after gastric resection and increased equally with patient age. Atrophic gastritis was more prominent after resection for gastric than for duodenal ulcer 10-13 years previously, but 20 years after the operation this difference was no longer significant. Hyperplastic polyps in the stomal region were found in 20% of cases 21-22 and 31-32 years postoperatively, but in only 4% after 10-13 years. Enterogastric reflux was endoscopically seen in most cases, but showed no clear correlation with the atrophic changes or polyps found in the gastric remnant mucosa. Endoscopic screening of all patients following gastric resection does not seem to be an effective method in selecting patients for further follow-up.