This study was undertaken to investigate the effect of cingulate cortical ablation upon gastric ulceration, and the pathway through which cingulate cortex exerts the effect. 56 female rats were divided equally into cingulate (cingulate cortical ablation), cingulate-vagal (cingulate cortical ablation and vagotomy), normal control and vagal (vagotomy) groups. Cingulate cortex was ablated through a slit-shaped opening (1 mm in width, 13 mm in length) which was made symmetrically on both sides of, and parallel to, the sagittal suture by removing a bone flap from parietal and frontal bones on each side. Vagus nerves on both sides were transected around the distal end of the esophagus. In the normal control animals, surgical intervention ended with scalp incision. All rats were kept without restraint or food deprivation for 3 weeks after surgery. The stomach of each rat was inflated with 7 ml of physiological saline and then removed under deep anesthesia. The mucosal surface was examined under dissecting microscope for the location, shape and number of ulcers, and then enlarged photograph (4X)was taken. The incidence of ulcer in each group was counted and the number of ulceration as well as the total area of glandular mucosa were measured on the photograph. Results obtained were as follows: 1. The mean number of ulcer per stomach and the total area of ulcer exprssed as permillage of the total area of glandular mucosa were significantly higher in the cingulate group than the cingulate-vagal, the normal control and the vagal groups. There was no difference among the latter three groups. 2. The incidence of ulcer in the cingulate group was significantly higher than that in the .normal control group and was also higher, though not significantly, than those in the cingulate-vagal and the vagal groups. There was no difference among the normal control, the cingulate-vagal and the vagal groups. It is inferred from the above results that the cingulate cortex exerts an inhibitory influence upon gastric ulceration and that this influence is mediated by controlling the vagal activity.