Omega-3 (omega-3) is an essential fatty acid (EFA) found in large amounts in fish oil. It contains eicosapentaenoic acid and docosahexaenoic acid (DHA). DHA is one of the building structures of membrane phospholipids of brain and necessary for continuity of neuronal functions. Evidences support the hypothesis that schizophrenia may be the result of increased reactive oxygen species mediated neuronal injury. Recent reports also suggest the protective effect of omega-3 EFA against neuropsychiatric disorders including schizophrenia. This study proposed to assess the changes in antioxidant enzyme and oxidant parameters in the corpus striatum (CS) of rats fed with omega-3 EFA diet (0.4 g/kg/day) for 30 days. Eight control rats and nine rats fed with omega-3 were decapitated under ether anesthesia, and CS was removed immediately. Thiobarbituric acid-reactive substances (TBARS) and nitric oxide (NO) levels as well as total superoxide dismutase (t-SOD) and xanthine oxidase (XO) enzyme activities in the CS were measured.