168 patients with duodenal or prepyloric ulcer, treated with parietal cell vagotomy (PCV), were followed up one to four years after operation. 67% of the patients had more than 5 years' history of ulcer disease and in 44% preoperative bleeding or perforation could be confirmed. According to the modified Visick classification the clinical results were considered excellent or very good in 71%, with a marked tendency to better results for those surgeons with the greatest experience in performing parietal cell vagotomy. The result was considered unsatisfactory in 25 patients (15%) and this was in all cases due to reoperation and/or recurrent ulcer. There was no postoperative mortality and a low frequency of postoperative complications. Dumping was found in only one patient and mild diarrhoea in two. At follow-up, 16 patients (9.5%) had had a proven and 8 (4.5%) a suspected recurrent ulcer and 3 had gastric retention without recurrence. The recurrence rate was very high for those patients operated during the first year after the introduction of PCV, but then decreased significantly. 18 patients required reoperation. Antrectomy or truncal vagotomy with drainage is considered the method of choice for patients with an incomplete PCV and recurrent ulcer.