Experimental autoimmune encephalomyelitis (EAE) was induced in a mouse model (C57/BL6) to investigate the antioxidant status of animals at various clinical stages of the disease. For this purpose, blood, brain and spinal cord samples from EAE mice were collected and examined at different scores following post-immunization with myelin oligodendrocyte glycoprotein (MOG). The clinical sign of mobility of animals on different days was associated with gradual increase in lipid peroxidation products (malondialdehyde, i.e. MDA) in brain and spinal cord. Changes in lipid peroxidation during EAE progression was inversely related to superoxide dismutase (SOD) activity in erythrocyte preparation. However, suppression of catalase in erythrocytes, tissue glutathione (GSH) and plasma total antioxidant capacity (FRAP assay) were the early events in EAE, occurred during scores 1 and 2. Biochemical alterations were corroborated with histopathological observations showing demyelination and inflammatory foci in central nervous system (CNS) of animals suffering from partial hind limb paralysis (score 3). These data suggest that generation of MDA in CNS is a continuous process during EAE induction and suppression of antioxidant factors are early events of the disease, but crucial in increasing the vulnerability of CNS to demyelinating lesions.