Background and Objective: Diazinon is one of the most widely used organophosphates (OPs) in agriculture. Toxic effects of diazinon are due to the inhibition of acetylcolinesterase, an enzyme needed for proper nervous system function. Investigates show that different classes of OPs may induce the production of free radicals and in cause disturbance in body antioxidant systems. The purpose of this study was to evaluate the effects of diazinon on oxidant-antioxidant system in the kidney of rat.     Materials and Methods: Wistar male rats were randomly divided into four groups including: control (corn oil as diazinon solvent) and three groups of diazinon receiving different doeses (30, 50 and 100 mg/kg) by intraperitoneal injection. 24 hours after injection, the rats to ether anesthesia and the kidney tissue was removed. The hemogenation, superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH), glutathione S-transferase (GST) activities, glutathione (GSH) and malondialdehyde (MDA) levels were determined through biochemical methods.     Results: The enhanced activities of CAT and SOD at doses higher than 30 mg/kg diazinon, and the increased MDA level at 100 mg/kg dose were observed whereas, the GSH level was significantly decreased comparing to the control group.No significant changes were observed with regard to GST and LDH activities.     Conclusion: Diazinon induces the production of free radicals and oxidative stress. The enhanced activity of antioxidant enzymes and depleted GSH content is indicative of oxidative tissue injury.