The toxicological effects of 10% glycerol were investigated in the mouse and rat. This product displayed very low acute toxicity on i.v. and intraperitoneal administration while no toxic effects were noted in the rat as a result of repeated administration over 3 months. Teratogenic effects were not observed after daily i.v. administration in the rabbit. Changes in arterial pressure and globular osmotic resistance did not appear during or after continuous infusion. The relevant literature is also examined. Glycerol has been found active in experimental various models of cerebral oedema. It also has a useful effect on cerebral metabolism.