gamma-Oryzanol has been reported to inhibit gastric secretion and experimental ulcers in rats. In this paper, the inhibitory effects of gamma-oryzanol on gastric secretions caused by three stimulants have been compared. gamma-Oryzanol was slightly effective for histamine-stimulated acid secretion, non effective for carbachol-stimulated secretion and significantly inhibited the tetragastrin-stimulated secretion. The effect of gamma-oryzanol on acid secretion stimulated by tetragastrin was prevented by vagotomy but not by splanchnicotomy. It is assumed that the gastric antisecretory effect of gamma-oryzanol is mediated by the vagus nerve which plays a role in the action of gastrin.