• Conditions that predispose a patient to hyperacidity, to anastomotic ulcer, and to the dumping syndrome after subtotal gastric resections have been studied in 100 patients who underwent the Billroth 2 operation. Recurrence of acidity after operation was less frequent in patients whose preoperative acidity had been normal than in those whose preoperative acidity had been high. The more extensive the resection, the less frequent was the occurrence of higher postoperative free acid titers. Anastomotic ulcers did not occur in 70 patients with the more extensive (more than three-fourths) resections but did occur in 4 out of 30 patients with the less extensive resections. These findings exhibited the advantages of the more extensive resections with or without vagotomy. The dumping syndrome was only a little more frequent in the patients with the more extensive resections. It was more strongly correlated with sensitiveness and tension in the patient. These facts affect the surgeon's decision as to the type of operation, how extensive it should be, and whether vagotomy should be done at the same time.