With the use of electromyography and intraluminal pressure recording of the pylorus, the effect of selective proximal and truncal vagotomy on the gastric motility was investigated in 10 dogs. The results are summarized as follows: 1. Control dogs showed regular discharge intervals with elevation of intrapyloric pressure coinciding with the action potentials. There was seen no occurrence of antiperistalsis. 2. Selective proximal vagotomy resulted in the prolongation of discharge intervals along with slight decrease in the incidence of action potentials. The rate of antiperistalsis was 4.4%. Besides, the rate of pyloric contraction also showed a tendency of slight decrease. 3. Truncal vagotomy lead to the prolongation of discharge intervals and decrease in the incidence of action potentials, though these changes were milder than those after selective proximal vagotomy. The incidence of antiperistalsis was 6.8% which was higher than the one after selective proximal vagotomy. Eelvation of intrapyloric pressure did not necessarily took place coinciding with the action potentials. Intrapyloric pressure as well as the incidence of pyloric contraction showed a marked decrease when compared with those of the control and selective proximal vagotomy dogs. Out of these results, it is concluded that the selective proximal vagotomy is superior to the truncal vagotomy when viewed from the preservation of the gastric motility.