In this study, the effect of streptozotocin (STZ) on lipid peroxidation and glutathione (GSH) content was investigated in the liver, pancreas and kidney of rats. Lipid peroxide levels were significantly increased in homogenates and mitochondrial fractions of the liver, kidney acid pancreas after STZ administration. GSH levels in hepatic acid pancreatic tissues were decreased but unchanged in the kidney of diabetic rats. GSH content in hepatic mitochondrial fraction was also decreased compared to control group. On the other hand, the destruction of pancreatic beta-cells was also observed histopathologically. Our results indicate that oxidative stress may play an important role in STZ induced diabetes and mitochondrial fraction may be the target in this toxicity.