Experimental autoimmune encephalomyelitis (EAE) is a well-established cell-mediated autoimmune inflammatory disease of the CNS, which has been used as a model of the human demyelinating disease. EAE is characterized by infiltration of the CNS by lymphocytes and mononuclear cells, microglial and astrocytic hypertrophy, and demyelination which cumulatively contribute to clinical expression of the disease. EAE was induced in female Sprague-Dawley rats, 3 months old (300 g ± 20 g), by immunization with myelin basic protein (MBP) in combination with Complete Freund's adjuvant (CFA). The animals were divided into 7 groups: control, EAE, CFA, EAE + aminoguanidine (AG), AG, EAE + N-acetyl-L-cysteine (NAC) and NAC. The animals were sacrificed 15 days after EAE induction, and the level of nitric oxide (NO(·)) production was determined by measuring nitrite and nitrate concentrations in 10% homogenate of cerebellum and spinal cord. Obtained results showed that the level of NO(·) was significantly increased in all examined tissues of the EAE rats compared to the control and CFA groups. Also, AG and NAC treatment decreased the level of NO(·) in all tissues compared to the EAE group. The level of NO(·) is increased significantly in the spinal cord compared to the cerebellum. The clinical course of the EAE was significantly decreased in the EAE groups treated with AG and NAC during the development of the disease compared to EAE group and its correlates with the NO(·) level in cerebellum and spinal cord. The findings of our work suggest that NO(·) and its derivatives play an important role in multiple sclerosis (MS). It may be the best target for new therapies in human demyelinating disease and recommend the new therapeutic approaches based on a decreased level of NO(·) during the course of MS.