Summary Pavlov type pouches in dogs were vagally denervated by transecting the muscular bridge, thus converting them into Heidenhain pouches. The effect of this form of vagal denervation on the secretion of acid and pepsin by the pouches in response to stimulation by histamine, gastrin, Urecholine, or combinations of these stimulants was studied. The studies were performed on two groups of dogs, one with intact, the other with resected antrum. Vagotomy reduced the maximal acid secretion in response to histamine, gastrin, and combinations of histamine or gastrin with Urecholine. The one exception to this statement was in the nonantrectomized dogs stimulated with histamine alone; in this instance the maximal acid secretion in response to histamine was not decreased. Acid secretion in response to submaximal doses of histamine, gastrin, and combinations of histamine or gastrin with Urecholine was significantly reduced by vagotomy in both the antrectomized and nonantrectomized dogs. Acid secretion in response to submaximal doses of Urecholine alone showed some tendency to increase after vagotomy. Vagotomy depressed the secretion of acid in response to gastrin more than in response to histamine. Urecholine produced greater augmentation of the maximal secretion of acid in response to gastrin than to histamine. The effect of vagotomy on the secretion of pepsin cannot be described by any simple generalizations; the nature of the stimulant and its dose and the presence or absence of the antrum were modifying factors. Two observations are noteworthy: 1) in the vagally denervated pouches (antrum intact) doses of gastrin that were maximal or supramaximal for acid secretion stimulated pepsin secretion, and 2) vagal denervation caused unequivocal supersensitivity of the pepsin stimulating action of Urecholine.