Toxic doses of Selenium (Se) (12.5 and 37.5 micro moles/Kg egg wt.) administered to 14 day old chick embryos reduced the level of lipid peroxides (LPO) significantly both in hepatic and brain tissues. However, the LPO formation was inhibited maximally at early hours after exposure (3 h and 6 h) and it was gradually increased thereafter to normal levels by 48 h. Further, the effect of Se on some of the antioxidant enzymes like glutathione peroxidase (GPx), glutathione transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD) and catalase were studied. In hepatic tissues GPx, GST and SOD activities were increased at 6 h post treatment with no change in the activities of GR and catalase. However, at 48 h GST and catalase activities were found to be increased, while GPx, GR and SOD activities were not affected. In brain at 6 h increase in the activities of GPx, GST, GR and SOD and no change of catalase were observed. At 6 h glutathione (GSH) levels were reduced in both hepatic and brain tissues. Our results suggest that the elevated levels of antioxidant enzymes at early hours were successful in bringing LPO levels back to normal.