The function of the stomach to store food, grind it, and release it slowly into the stomach is reviewed. The functional regions of the stomach—fundus, body, and antrum—are discussed. Receptive relaxation and gastric accommodation of the fundus are described, and the mechanisms that bring these about. The cardiac pacemaker is described. Gastric motility is discussed along with gastric emptying and the enterogastric inhibitory reflex and the function of GI hormones cholecystokinin and secretin. The migrating motility complex or migrating myoelectric complex during the interdigestive period is described. Stomach secretions are considered, beginning with a description of the secretory glands and cells. Secretion of mucus by neck cells, pepsinogen by chief cells, and HCl and intrinsic factor by parietal cells is discussed. The mechanism of acid secretion is covered and its regulation by nerves, hormones, and paracrine substances such as histamine.