Abstract: Gentianine is an alkaloid isolated from the root Of Gentiana macrophylla.It has been shown that the alkaloid has an inhibitory effcct on experimental "arthritis" in rats, and that the anti-inflammatory effect is mediated through the activation of the pituitary- adrenal system. In the present paper the effect of gentianine on the blood sugar level of rats and mice is reported. Intraperitoneal injections of gentianine to rats in doses of 180 or 250 mg/kg caused a rise of the blood sugar level. The effect began to appear half an hour after the in- jection and lasted for about three hours. Mice also responded with a rise of the blood sugar to the intraperitoneal injections of gentianine at dosages of 150-250 mg/kg. In adrenalectomized rats or mice, the effect of gentianine on blood sugar failed to appear. Concurrent with the rise of blood sugar level, gentianine caused a marked depletion of liver glycogen in mice. Pretreatment of mice with ergotamine blocked the effect of gentianine on blood sugar. Obviously, gentianine raises the blood sugar level in animals under conditions that their adrenals are intact, and this effect is probably mediated through adrenaline secretion.