Forty-five patients with burn area exceeding 30% TBSA were studied prospectively. Among these 45 patients, 13 developed multiple organ failure (MSOF). Blood superoxide, dismutase (SOD) activity and plasma malondialdehyde (MDA) levels were sequentially determined to assess the role of excessive release of oxygen radicals and lipid peroxidase injury in the mechanism of pathogenesis of postburn MSOF. The results showed that the anti-oxidation capacity of the body was markedly depressed and lipid peroxidase injury markedly increased after a severe burn injury. These changes were not only related to hypovolemic shock after the injury, but also the severity of the burn injury and infection.