The levels of the lipid peroxidation product malondialdehyde (MDA) and the activity of transaminases and alkaline phosphatases were estimated in the sera of 25 thermally injured patients at various time intervals after injury. The level of MDA was increased during the early postburn period, whereas the activities of transaminases and alkaline phosphatase became elevated later after injury. It is concluded that an increased concentration of lipid peroxidation product (MDA) in the early postburn period may affect the spleen, liver and kidney, resulting in the release of enzymes into blood stream. Such damage may be checked by the antioxidants superoxide dismutase or allopurinol.