Objective.. To investigate the effect of co-exposure to LPS and heat on plasma malondialdehyde （MDA） content and superoxide dismutase （SOD） activity in rats. Methods： Male specific pathogen-free Wistar rats were randomly assigned to the following groups., saline injection＋normothermic control （C-Group）, saline injection＋heat exposure （H-Group）, LPS injection＋normothermic control （L-Group）, and LPS injection＋heat exposure （HL-Group）. Rats in H-/HL-Group were exposed in a chamber at an ambient dry bulb temperature （Tdb） of （35.0±0. 5）℃ and in C-/L-Group at an ambient Tdb of （26.0＋0.5） ℃. Rats in L-/HL-Group were given an intravenous injection of LPS 10 mg/kg via tail veins to induce endotoxemia and in C-/H-Group were given an intravenous injection of 0. 9% NaCl （10 ml/kg） via the tail vein. Mean arterial pressure （MAP） was continually monitored in all rats. Plasma levels of MDA and SOD activity were determined at 0, 40, 80, 120 rain after exposure. Results： There was significant difference in plasma MDA levels and activities of SOD between L-/H-/HL-Group and C-Group （P〈0.05）. The rats in HL-Group displayed significantly increased MDA level and decreased SOD activity compared with those in the other 3 groups（P〈0.05）. Conelusion. This study suggests that co-exposure to LPS and heat can promote and augment systemic inflammatory response syndrome in rats.