Abresham or silk cocoon (Bombyx mori), a well known Unani drug has been previously shown by us to possess striking antilipidperoxidative and ROS generation blocking potential in rats subjected to oxidative stress by immobilization. This effect is likely to be produced by an increase in the concentration of GSH following silk cocoon administration, as it contains a higher concentration of those three amino acids viz. Gglycine, Glutamic acid and Cysteine, which constitute the glutathione and by modulating the activities of its metabolizing enzyme which are responsible for the reduction of oxidized glutathione and break down of GSH. Therefore, in present study silk cocoon was studied for its effects on the level of GSH, GR, GGT and GST in rat subjected to oxidative stress by immobilization. It produced a significant increase in GSH concentration and GR activity and a significant decrease in GGT activity in a dose dependant manner. It can be concluded that silk cocoon exerts antioxidant activity by increasing glutathione and by modulating its metabolizing enzyme.