THE ANTIOXIDANT effect of Sumac; Rhus coriaria L. against whole body gamma-irradiation-induced oxidative damage in lung and liver tissues was investigated in albino rats. To achieve the ultimate goal of this study, 48 adult rats were randomly divided into 4 groups of 12 animals each. Group I: Control group. Group II: Irradiated with a single dose of 5Gy γ-rays. Group III: Fed with sumac orally (300 mg/ kg body wt/ day) for 10 days. Group IV: Fed sumac (300 mg/ kg body wt) for 3 days pre-irradiation and 7 days after-radiation (5 Gy). The rats were sacrificed 1 and 7 days after a single exposure to γ-rays. The animals exposed to gamma radiation recorded significant increase in malondialdehyde (MDA) and total nitrate oxide (NO) levels in both lung and liver tissues. Also the results revealed, significant decrease in the activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSHPx) and the level of reduced glutathione (GSH), in lung and liver tissues. Moreover, a significant increase in plasma glucose accompanied with a significant decrease in insulin level was observed in irradiated rats. Administration of sumac for 10 days to rats prior and post gamma irradiation improved the tested parameters except glucose. In conclusion, data obtained from this study indicated that sumac could increase the antioxidant defence mechanism in rat and there by protects the animals from radiation-induced organs toxicity but it may increase the blood sugar, therefore in diabetic patient be considered.