Forty patients with duodenal ulcer who underwent selective proximal vagotomy (SPV) with pyloroplasty were examined of intestinal metaplasia before operation, with no increase staining methods, before and after operation. Follow-up periods were between 2 and 9 years after SPV. Reduction rates of acid secretion by SPV were 79% in BAO and 62% in MAO. Five patients were observed to have a slight degree of intestinal metaplasia before operation, with no increase after operation. In the remaining 35 patients, staining areas were not observed either before or after operation. The acid-secreting area demonstrated by endoscopic congo red staining tended to become atrophic after SPV. It can be concluded that the reduction of gastric secretion by SPV does not result in rapid development or progress of intestinal metaplasia of the gastric mucosa.