METHODS Experimental animal model to assess ischemic spinal cord injury following occlusion of the thoraco-abdominal aorta. OBJECTIVE To measure whether melatonin administered to rabbits before and after occlusion exerts an effect on the repair of ischemia-reperfusion (IR) injury. METHODS Medical Biology Laboratory, Inonu University, Malatya, Turkey. METHODS Rabbits were divided into three IR treatment groups and one sham-operated (ShOp) control group. The three treatment groups had their infrarenal aorta temporarily occluded for 25 min, while the ShOp group had laparotomy without aortic occlusion. Melatonin was administered either 10 min before aortic occlusion or 10 min after the clamp was removed. Physiologic saline was administered to the control animals. After treatment, the animals were euthanized and lumbosacral spinal cord tissue was removed for the determination of relevant enzyme activities. RESULTS Malondialdehyde levels, indicating the extent of lipid peroxidation, were found to be significantly increased in the nonmelatonin treated (IR) group when compared to the ShOp group. Melatonin, whether given to pre- or post occlusion groups, suppressed malondialdehyde levels below that of the ShOp group. Catalase (CAT) and glutathione peroxidase (GSH-Px) enzyme activities were increased in the IR group compared to the ShOp group. Melatonin given preocclusion resulted in a significant decrease in both CAT and GSH-Px enzyme levels. The superoxide dismutase (SOD) enzyme activity was decreased in the ischemia-reperfusion treatment group. However, the melatonin treatment increased SOD enzyme activity to levels approximating that of the ShOp group. CONCLUSIONS To our knowledge, this is the first study that shows the effects of melatonin administered both pre- and postischemia on induced oxidative damage to injured spinal cords. Our data also expands on reports that melatonin administration may significantly reduce the incidence of spinal cord injury following temporary aortic occlusion.