The stomach is innervated by both parasympathetic and sympathetic neurons of the autonomic nervous system. Vagal stimulation, broadly, increases the secretory and motor function of the stomach. This chapter discusses the effect of vagal stimulation on gastric secretion. The important role of the nervous system in regulating gastric acid secretion has long been recognized, with prior studies demonstrating that the vagus was the sole responsible gastrocephalic neural link. Vagal stimulation of the parietal cell appears to involve several mechanisms. The parietal cell possesses several different receptors for stimulatory and inhibitory ligands on its basolateral membrane. Autocrine or paracrine signaling by sonic hedgehog (Shh) is required for full functional differentiation of the parietal cell, as well as gastric acid secretion. The H+/K+ adenosine triphosphatase (H+, K+‐ATPase) enzyme of the gastric parietal cell is generally regarded as the most critical component of the ion transport system mediating acid secretion.