In a prospective randomized trial parietal cell vagotomy (PCV) was compared with truncal vagotomy with drainage (TV) in the treatment of duodenal ulcer. The material consists of 106 patients, 50 TV and 56 PCV. Basal and maximal acid output (BAO, MAO) were measured preoperatively, 6 weeks and 12 months postoperatively. The clinical results were judged from a modified Visick grading system 1-6 years postoperatively. BAO 6 weeks after PCV was reduced with 60% in average and 12 months postoperatively with 45%. After TV the BAO was reduced with 53% 6 weeks postoperatively and 34% 12 months postoperatively. MAO was reduced with 47% 6 weeks after PCV and with 31% 12 months postoperatively. After TV the reduction of MAO was 50% and 44%, respectively. After PCV 62% of the patients were insulin positive at the first postoperative examination and 78% one year later. After TV 46% of the patients had a positive insulin test at the first postoperative examination and 50% one year later. In the PCV group 9 patients (16%) have got recurrences during the 1-6 years observation time, in the TV group there were 4 recurrences (8%). In the PCV group 24% of the patients with pyloric or prepyloric ulcer got recurrences and 13% of the patients with duodenal ulcer. In the TV group the number of recurrences was 13% and 6%, respectively. At the modified Visick classification 71% of the patients in the PCV group were graded as I and II, 4% as III and 25% graded as IV. After TV 83% of the patients were graded as I and II, 4% as III and 13% graded as IV. The results from this study do not allow us to recommend PCV before TV and it should be seriously questioned if it shall at all be performed on prepyloric ulcers.