Graded acid secretory responses were obtained in anesthetized cats with intact pyloric region when the frequency of electrical stimulation of the neck vagi was increased from 0.5 to 8 Hz; 4-8 Hz induced maximal acid secretion. Antrectomy reduced the response to vagal stimulation but the reduction reached statistical significance only after additional resection of the duodenum. Administration of per se subthereshold or threshold doses of exogenous gastrin restored the acid response to vagal stimulation in antrectomized cats. Combination of a high dose of histamine and vagal stimulation in antrectomized output in anaesthetized cats which roughly amounted to two thirds of the reported maximal acid secretory rate during histamine stimulation in non-anaesthetized cats. The present results suggest that the physiological vagal discharge rate to the acid secreting glands does not reach higher frequencies than aroung 8 Hz. It is also suggested that an intact antroduodenal region is essential for acid responses to physiological vagal stimulation in the cat. Finally, the reduced sensitivity to gastric secretory stimulants under anaesthesia appears to be due in part to a reduced vagal tonus.