In order to investigate the frequency of postgastrectomy syndrome in patients with benign gastroduodenal diseases who gastrectomized partially, the authors studied the case records of consecutive 100 such patients treated at this institute. The results obtained were as follows. 1) Concerning postoperative diagnosis, 55 patients were diagnosed as ulcus ventriculi; 22, ulcus duodeni; 4, ulcus vent. et duodeni; 10, gastric hyperacidity only; 4, perigastric adhesion; 2, ptosis ventriculi; 2, gastric polyp; 1, duodenal diverticulum. 85 patients were male; 15, female. Concerning operative method, 21 patients were operated on Billroth I procedure; 19, Billroth II antecolica oralis inferior with Braun's anastomosis; 60, Billroth II oralis inferior. 2) Of 28 patients with postgastrectomy syndrome, 9 patients had early postprandial syndrome; 6, late postprandial syndrome; 6, postoperative gastric atonia; 2, afferent loop syndrome; 1, obstruction of efferent loop; 2, intestinal adhesion; 2, ulcer of anastomosed site. 3) In our series, there were no significant difference in frequency of postgastrectomy syndrome between B. I and B. II procedure, but postgastrectomy syndrome of patients with B. II were more severe than that of patients with B. I. 4) Of 72 patients without postgastrectomy syndrome, 69,7% (50 patients) continued to gain weight postoperatively, but of 28 patients with postgastreetomy syndrome 28,5% (8 patients) gained weight postoperatively.