In the view of the importance of esterified and free cholesterol in lipid metabolism, as well as serum transaminase activity in the liver, the present study was designated to elucidate the effects of whole body X-irradiation on the levels of esterified cholesterol, free cholesterol and activity of serum transaminase in mouse. Also, in order to observe possible radioprotective action of reduced glutathione, a combination of X-irradiation and injection of GSH was done to see the effects of GSH on lipid metabolism.