Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) that leads to an inflammatory demyelination, axonal damage, and progressive neurologic disability that affects approximately 2.5 million people worldwide. The aim of the present research was to test the therapeutic effect of Aloe vera in experimental model of MS. All experiments were conducted on C57BL/6 male mice aged 6-8 weeks. To induce the experimental autoimmune encephalomyelitis (EAE), 250 microg of the myelin oligodendrocyte glycoprotein 35-55 peptide emulsified in complete freund's adjuvant was injected subcutaneously on day 0 over two flank areas. In addition, 200 ng of pertussis toxin in 100 microL phosphate buffered saline was injected intraperitoneally on days 0 and 2. The therapeutic protocol was carried out intragastrically using 120 mg/kg/day Aloe vera from 7 days before to 21 days after EAE induction. The mice were killed 21 days after EAE induction. The brains of mice were removed for histological analysis and their isolated splenocytes were cultured. The results indicated that treatment with Aloe vera caused a significant reduction in severity of the disease in experimental model of MS. Histological analysis showed 3 +/- 2 plaques in Aloe vera-treated mice compared with 5 +/- 1 plaques in control group. The density of mononuclear infiltration in the CNS of Aloe vera-treated mice (500 +/- 200) was significantly less in comparison to 700 +/- 185 cells in control group. Moreover, the serum level of nitric oxide in treatment group was significantly less than control animals. The level of interferon-gamma in cell culture supernatant of treated mice splenocytes was lower than control group, whereas decrease in serum level of interleukin-10 in treatment group was not significant in comparison with control mice. These data indicate that Aloe vera therapy can attenuate the disease progression in experimental model of MS.