The perfusion method was used to study the reaction of the vessels in the rabbit ear, isolated on the 1st–4th day after local irradiation with a dose of 100 R. The effect was most pronounced one day after the irradiation, and was manifested by the disappearance of the spasm and dilatation of the vessels. In response to adrenalin administration, the vessels of the irradiated rabbit ear showed a more profound and more prolonged constriction than that seen in the control, followed by subsequent dilatation.