The incidence and degree of bile reflux and gastritis has been measured in normal subjects and in patients with gastric ulcer before operation and after treatment by highly selective vagotomy with ulcer excision, Billroth 1 partial gastrectomy, and truncal vagotomy and drainage. Before operation patients had significantly higher (P less than 0.001) bile acid concentrations in the stomach than normal subjects. Treatment by highly selective vagotomy resulted in significantly lower bile acid concentrations than those before operation and those found after Billroth 1 partial gastrectomy. Antral and body gastritis was significantly less in normal subjects than in the preoperative and all postoperative groups. There was no significant difference in antral or body gastritis between the preoperative gastric ulcer patients and the patients after any of the surgical procedures despite the significant differences in bile acids. Though highly selective vagotomy in the treatment of gastric ulcer results in a reduction in duodenogastric reflux of bile there is no improvement in the gastritis that is present.