Effect of aloctin A, glycoprotein isolated from leaves of Aloe arborescens MILL, on gastric secretion and on acute gastric lesions in rats were examined. Aloctin A given intravenously dose-dependently inhibited the volume of gastric juice, acid and pepsin output in pylorus-ligated rats. Aloctin A given intravenously significantly inhibited the development of Shay ulcers and indomethacin-induced gastric lesions in rats. It also inhibited water-immersion stress lesions induced in pylorus-ligated rats.