The generation of the reactive oxygen metabolites plays an important role in the pathogenesis of irradiation-induced tissue injury. Resveratrol, a polyphenolic phytoalexin, is one of the most extensively studied natural products, with wide ranging biological activity and tremendous clinical potential (1). First identified from fruits and plants, in particular grapes and wines, its most noticeable effects are its anti-thrombogenic, anti-inflammatory, cardio-protective, neuro-protective, anti-aging, and cancer preventive and therapeutic activities (2, 3). The objective of this study was to examine the potential radioprotective properties of resveratrol (RVT) against irradiation-induced oxidative damage in the ileum and liver. Sprague-Dawley rats were exposed to irradiation (LINAC producing 6 MV photons at a focus) after a 10-days pretreatment with either saline or RVT (10 mg/kg/day) given orally, and treatments were repeated for 10 more days after the irradiation. Under ketamine anaesthesia (100 mg/kg intraperitoneally), each rat received a single whole-body X-ray irradiation of 800 cGy. Animals were returned to their home cages following irradiation. After decapitation, ileum and liver samples were obtained for the determination of tissue malondialdehyde (MDA; an index of lipid peroxidation) and glutathione (GSH, an antioxidant) levels, myeloperoxidase activity (MPO; an index of tissue neutrophil accumulation) and collagen contents. Tissues were also examined microscopically. Lactate dehydrogenase (LDH), an indicator of tissue damage, and tumour necrosis factor-alpha were assayed in serum samples. Irradiation caused a significant decrease in GSH, which was accompanied by significant increases in MDA levels, MPO activity, and collagen content of the tissues studied (P<0.05-0.001). Similarly, serum TNF-alpha and LDH were elevated in the irradiated rats as compared with the control group. On the other hand, RVT treatment reversed all these biochemical indices, as well as histopathological alterations induced by irradiation. Our results suggested that RVT supplementation reduces oxidative damage in the ileal and hepatic tissues probably by a mechanism that is associated with the decreased production of reactive oxygen metabolites and enhancement of antioxidant mechanisms. Thus, it may be suggested that supplementing cancer patients with adjuvant therapy of RVT may have some benefit for a more successful radiotherapy.