The relative merits of proximal gastric vagotomy (PGV), truncal vagotomy with drainage (TV + D), and truncal vagotomy with antrectomy (TV + A) in the treatment of chronic duodenal ulcer were evaluated and compared in 152 patients in a prospective, randomized and controlled clinical trial. One death occurred after TV + A, resulting in an operative mortality of 2% after gastrectomy and 0.7% for the entire series. After one to six years, stomal and duodenal ulcers proven by endoscopy occurred in eight patients after PGV (16%) and in six patients after TV + D (11.8%); the difference was not statistically significant (p greater than 0.5). One additional patient developed a gastric ulcer nine months after PGV. There was so far no ulcer recurrence after TV + A. Majority (13 patients) of the recurrent ulcers were discovered within three years after surgery. Patients after PGV experienced significantly less unwanted side effects than those after either TV + D or TV + A; particularly, dumping, epigastric fullness, and diarrhea. When the functional status was graded according to a modified Visick system that excluded ulcer recurrence, significantly more PGV patients were placed in the near-perfect grade (82.1%) than TV + A patients (58%). Patients after TV + D fared better than patients after TV + A; but the differences were not significant. However, when ulcer recurrence was included in the functional assessment, the advantage of PGV was lost.