In order to delineate the role of enterogastric reflux in changes of postoperative gastric secretory functions, 22 patients with peptic ulcers, who were randomly assigned to partial gastrectomy without vagotomy with either Billroth II or Roux-en-Y anastomosis, were prospectively studied before and 6 months after surgery. Preoperatively, there were no significant differences in gastric secretory functions between the two groups of 11 patients. Postoperatively, median fasting bile acids in the stomach increased in the Billroth II patients from 0.35 to 16.10 mumol/hr (p less than 0.01), but significantly decreased in the Roux-en-Y patients from 0.30 to 0.10 mumol/hr (p less than 0.05), which indicated adequate prevention of enterogastric reflux after the Roux-en-Y procedure. Gastrectomy resulted in significant reductions of median values of basal acid output (4.6 vs 0.6 mmol/hr, p less than 0.01, and 4.2 vs 0.4 mmol/hr, p = 0.02), peak acid output (31.6 vs 4.2 mmol/hr, p less than 0.01, and 38.7 vs 4.5 mmol/hr, p less than 0.01), serum pepsinogen A (121 vs 86 micrograms/L, p less than 0.01, and 92 vs 45 micrograms/L, p less than 0.01), meal-stimulated serum gastrin secretion (1472 vs 199 pM.60 min, p less than 0.0001, and 1017 vs 199 pM.60 min, p less than 0.0001) in the patients with Billroth II and Roux-en-Y anastomosis, respectively. There were, however, no significant differences in gastric secretory parameters between the two groups when studied 6 months after surgery. Therefore it is concluded that after gastrectomy, enterogastric reflux does not affect the secretory function of the gastric remnant within the first 6 months after surgery.