Large amounts of gastrin are present in vagally induced gastric juice of cats. This gastrin is secreted directly into the gastric lumen from the antral mucosa, because in experiments in which the stomach was divided into one antral and one corporeal pouch, most of the gastrin appeared in the antrum, only small amounts appearing in the acid gastric juice. When the antrum was perfused with a slightly alkaline buffer solution, parallel recordings of the gastrin release into the antral lumen and into the gastric venous outflow revealed more gastrin to be secreted per minute into the gastric lumen than into the blood (2 to 23 times as much). Electrical vagal stimulations caused an increased release of gastrin both into the antral lumen and into the circulation.