The vagus nerve plays a central role in the regulation of gastric acid secretion and gastrin release. The current understanding of the mechanisms involved in vagal regulation of acid secretion and gastrin release is reviewed. Thyrotropin-releasing hormone from the medullary raphe nuclei appears to be the central excitatory mediator of vagal action in the dorsal motor nucleus. Vagal stimulation of the parietal cell occurs through M3 cholinergic receptors and via the release of histamine and gastrin from enterochromaffin-like cells and G-cells, respectively. Somatostatin exerts a tonic basal inhibition of both the parietal cell and the G-cell. Vagal stimulation suppresses somatostatin release from delta cells, thereby "disinhibiting" these cells.