Since the Roux-en-Y anastomosis prevents the sequela of postoperative enterogastric reflux after gastrectomy, this approach has been advocated as the primary procedure in patients undergoing gastrectomy for peptic ulcer. We have prospectively followed for 2 years 22 patients, in whom gastrectomy was performed with, at random, either Roux-en-Y (n = 11) or Billroth II (n = 11) anastomosis. Two of the 11 patients who had received the Roux-en-Y procedure had anastomotic ulcers, leading to reresection in one of them. These two patients were found to have the highest values for basal and pentagastrin stimulated gastric acid output. After the Billroth II procedure a single patient had a small anastomotic ulcerative lesion. Apart from differences in intragastric bile acids (p less than 0.0001) and the gastritis activity score (p less than 0.01), no significant differences were found between the patients with Roux-en-Y and Billroth II anastomosis with respect to basal and pentagastrin-stimulated gastric acid secretion, basal, postprandial and bombesin-stimulated serum gastrin secretion, serum pepsinogen A and C concentrations, the serum pepsinogen A/C ratio, postprandial glucose, and for a modified Visick grading. From this small series we conclude that, as compared with the Billroth II-anastomosis, the Roux-en-Y procedure effectively prevents enterogastric reflux, and is associated with a higher gastritis activity score, but not with differences in gastric acid, gastrin, pepsinogens, or Visick grading. Furthermore, inadequate reduction of acid secretion in some patients after the Roux-en-Y procedure may lead to recurrent peptic ulcers.