The synthesis and the utilization of noradrenaline in the caudal and cranial part of intact and sectioned rat spinal cords were determined at 20 h or for 30 min--2 h after an operation. The synthesis and the utilization of noradrenaline in the caudal part of spinal cords transected 20 h previously were retarded as compared to those in the cranial part of sectioned cords or in the caudal part of intact cords. The synthesis of noradrenaline was stimulated in the caudal part of the spinal cord when measured for 30 min after a transection. The utilization of noradrenaline in the spinal cord caudal to a transection was not decelerated during 2 h after an operation. Local application of lidocaine to the cord prior to the cut changed the synthesis and the utilization of noradrenaline in both parts of the spinal cord to values similar to those obtained 20 h after the operation. Transection of the spinal cord might stimulate the synthesis and the utilization of noradrenaline by a shortlasting mechanical irritation of neurons cut by the lesion.