In this study, we investigated the effect of L-carnosine (CAR) on prooxidant antioxidant balance in several tissues of rats exposed to chronic stress. Both cold and immobilization stresses were applied to rats at the same time. In the stress group, rats were placed in restraint cages and kept in a cold room (+4 degrees C) for I h for 21 days (5 days a week). Rats were injected with CAR (250 mg/kg, i.p.) at 30 min before stress application. Malondialdehyde, diene conjugate, protein carbonyl and nitrotyrosine levels, nonenzymatic (glutathione, vitamin E, and vitamin C), and enzymatic (catalase, superoxide dismutase and glutathione peroxidase) antioxidants were determined in the liver, heart, and brain tissues. Chronic cold plus immobilization stress was observed to affect especially the prooxidant antioxidant status in the brain tissue of rats. This is the first report showing the beneficial effects of CAR on oxidative stress in the brain in rats exposed to stress.