Distension of the isolated mouse stomach stimulated gastric acid secretion. Atropine, cimetidine, or proglumide antagonized the actions of cholinomimetics, histamine, and gastrin, respectively. However, these antagonists and the nerve blocking agent, tetrodotoxin, were without effect on basal secretion or distension-stimulated secretion. It is concluded that in the isolated mouse stomach neither basal secretion nor secretion evoked by distension involve the release of any of the established "physiological" secretagogues or the activation of intramural nerves.