Carbon dioxide inspired as a 40% mixture in oxygen and halothane protected the spinal cords of 5 rabbits subjected to 30 min of surgically created spinal cord ischemia. Spinal cord ischemia was produced in 20 New Zealand White rabbits by transection of four of the five pairs of segmental arteries arising from the abdominal aorta below the renal arteries plus temporary occlusion of the remaining pair. The artery was occluded for 15 min in 9 control rabbits, for 30 min in 6 control rabbits, and for 30 min in 5 treated rabbits after inhalation of 40% carbon dioxide. The extent of spinal cord injury was assessed by examining the rabbits for permanent loss of sensory and motor function in the hindlimbs and was compared in the treated and control groups. These results have implications for the management of patients subjected to aortic occlusion.