Thirty symptomatic patients with retained gastric antrum proved pathologically and/or by isotopic visualization were studied and treated from 1968 to 1983. The latent periods from the antral exclusion to the occurrence of anastomotic ulcers after a subtotal gastrectomy with Billroth's type II reconstruction varied from a few days to 19 years, with an average of 2.8 years. Fasting serum gastrin levels were normal in 14 of 21 patients and were intermittently high in some patients. The basal to maximal acid-output ratio was greater than 0.6 in 69% of the patients; primary cimetidine treatment was effective in three of five patients. Thirty-five operations on 27 patients were divided into six groups; all of these 27 patients eventually underwent resection of retained gastric antrum. We concluded that resection remains the best treatment for anastomotic ulcer related to retained gastric antrum. Additional truncal vagotomy did not provide additional benefit to these patients. Furthermore, cimetidine can be useful to control the symptoms for preoperative preparation or definitive treatment in high-risk patients.