Thermal injury initiates systemic inflammatory reactions producing burn toxins, an inflammatory response, oxygen radicals and finally peroxidation. The relationship between the amount of products of oxidative metabolism and natural scavengers of free radicals determines the outcome of local and distant tissue damage, and further organ failure in burn injury. To determine the relationship between the level of total natural scavengers of the body, the place of superoxide dismutase in this capacity, and its relation with lipid peroxidation, malondialdehyde, superoxide dismutase levels and total antioxidant status were measured in plasma. Animals were subjected to 30 per cent full thickness body surface area burn, and their blood was collected at 24 h postburn. Plasma malondialdehyde levels were significantly elevated above the level of controls (P < 0.02). Burn injury caused a remarkable decrease in superoxide dismutase (45 per cent decrease, P < 0.0001) and total antioxidant status (14 per cent decrease, P < 0.01) when compared to control. (C) 1997 Elsevier Science Ltd for ISBI.