The eradication of Helicobacter pylori (Hp) is known to reduce the recurrence rate of duodenal ulcer (DU) to similar extent as gastrectomy but it is not clear what is the prevalence of Hp in DU patients after surgical interventions such as gastrectomy or vagotomy. The purpose of this study was to evaluate the influence of gastrectomy or truncal vagotomy with pyloroplasty on the prevalence of Hp in 51 DU patients just before and 6-8 months after these procedures. Using C14-urea breath test (UTB), rapid CLO-test and histology of the biopsy samples of gastric mucosa obtained during gastroscopy, the Hp was detected in all DU subjects submitted to operation. Following distal gastric resection (antrectomy) with Billroth II anastomosis (N = 32) due to an ulcer resistance to conservative therapy, peptic ulceration was not observed during 6-8 months in any of the examined subjects and the Hp was only rarely observed (only in 3 out of 32 operated patients). Histologically, in antral biopsies taken prior to surgery, all DU patients presented chronic active gastritis. After the surgery, the absence of Hp was confirmed also by histology. Histological evaluation of gastrectomy stump biopsies revealed typical chronic gastritis with concomitant foveolar hyperplasia and focal gland dilation. Following selective vagotomy and pyloroplasty (N = 19), the scarring of duodenal bulb (without active ulcer) was seen in 4 out of 19 operated patients but the Hp was detected in all (100%) cases. Gastric biopsies prior and after vagotomy revealed chronic active gastritis associated with Hp infection. Basal plasma gastrin was reduced after gastrectomy by about 30% and basal and maximal pentagastrin-induced acid secretion was decreased by about 60% and 70%, respectively. Vagotomy did not reduce activity of the mucosal inflammation and the incidence of Hp. Basal plasma gastrin level was increased by about 60%, while basal and pentagastrin induced acid secretion was decreased by 25% and 40%, respectively. Because of the high ulcer recurrence rate after vagotomy as opposed to low recurrence after gastrectomy, it is reasonable to conclude that (1) the disappearance of Hp and reduction in plasma gastrin and gastric acid secretion were probably the major factors responsible for the high efficacy of gastrectomy in prevention of ulcer recurrence, (2) in non-complicated DU, gastric surgery should be avoided and replaced by conservative anti-Hp therapy involving both antisecretory or bismuth agents and antimicrobial drugs which should provide similar therapeutic effects as surgery and (3) vagotomy should be eliminated as the method of treatment of DU because of the high recurrence of peptic ulceration and the failure of this procedure to affect the Hp status.