In 38 patients who had been operated for peptic ulcer (32) or gastric cancer (6), we performed upper GI endoscopy with biopsies. HP was found in the mucosa in 8 out of 10 patients with highly selective vagotomy, 5 out of 11 patients with gastrectomy for ulcer, 6 out of 11 patients with vagotomy-pyloroplasty and in only 1 case out of 6 with gastrectomy for cancer. These results are in agreement with other publications. Bilio-pancreatic reflux into the stump probably explains why HP was found in only 50% of cases with suppression of pyloric function, compared with 80% after highly selective vagotomy. Interstitial gastritis was present in every case infected with HP, but the same gastritis was present in one half of mucosas, without infection by HP. This particular gastritis in probably caused by reflux. The role of HP in the relapse of ulcers therefore remains to be demonstrated.