The aim of the present study is to investigate the effect of different concentration of antioxidants on oxidative stress in rats fed on an oxidized oil. Sunflower oil was submitted to fryer treatments at temperature between (180-190 °C) on intermittent periods for 24 hrs. The changes in chemical properties of frying oil compared to fresh sunflower oil were investigated. Data illustrate the presence of an increase in acid value, peroxide value, polymers and a decrease in iodine number. Fatty acids constituents of this tested oil were also investigated. Fifty-four rats weighing approximately 100 grams each were divided into nine groups, each group containing six rats. Groups S2 and S3 fed on diets containing oxidized oil (15 %) and the other groups S4, S5, S6 S7, S8 and S9 fed on the same diet used in group S2 and supplemented with different concentration of antioxidants BHT (.02 gm/100gm oil), sodium selenite (1.5 mg / kg diet), p-carotene (10 mg/200gm rat/day), anthocyanin (1.43mg/200gm rat/day), cinnamon essential oil (0.9 gm/100 gm oil ) and clove essential oil (0.9 gm/100 gm oil) respectively. Rats fed oxidized oil (S2 and S3) had higher concentrations of cholesterol, LDL-cholesterol and triglycerides. Although, the concentration of total thyroxine in plasma of rats fed oxidized diet (S2 and S3) was higher than rats fed the oxidized oil and supplemented with different concentrations of antioxidants. The damage caused by the oxidized oil was revealed by a significantly rise in lactic acid dehydrogenase activity ( LDH ) and thiobarbituric acid reactive substances (TBARs ) in plasma of rats in groups S2 and S3 Compared to other groups (S4, S5, S6 S7, S8 and S9). On the other hand, BHT as synthetic antioxidant at 200 ppm induced significant decrease in TBARs and increase in the LDH activity and function (liver and kidney). Microscopical examinations of thyroid gland , heart , liver and kidney tissues of rats treated with natural antioxidants had the histological characters as that of the control rats whilst, the treatment of BHT at 200 ppm altered the features of rat liver, kidney, thyroid gland and severely damaged rat heart tissues.