Chemokines may play a role in the pathogenesis of multiple sclerosis (MS), facilitating the traffi cking of immune cells across the blood-brain barrier. Interferon-inducible T cell alpha chemoattractant (CXCL11) recruits activated Th1 cells to sites of infl ammation. We have estimated the levels of CXCL11 chemokine and IL-18 also known as IFN-gamma inducing factor in sera of 30 relapsingremitting MS patients during relapse, both before and after methylprednisolone (MP) treatment and compared the results with those in control group. The serum CXCL11 and IL-18 concentrations were measured by the ELISA method. The serum levels of CXCL11 were detectable in 23 relapsing-remitting MS patients. The levels were signifi cantly higher in sera of studied patients before (55.4 ± 63.1 pg/ml) and after steroid therapy (40.7 ± 43.2 pg/ml) in comparison with control group (17 ± 18.3 pg/ml, P=0.002). The serum levels of CXCL11 before and after MP treatment did not differ signifi cantly. The levels of IL-18 were detectable in the sera of all studied MS patients. The serum concentration of IL-18 in relapsing-remitting MS patients before MP therapy was 246.6 ± 143.5 pg/ml and was signifi cantly higher than the level of IL-18 in healthy controls (171.06 ± 56.8 pg/ml, P=0.008). IL-18 levels in the sera of MS patients after steroid therapy was 258.76 ± 292.5 pg/ml and was higher than that in the control group (P=0.006) but did not differ signifi cantly from the serum concentration of IL-18 in the same patients before the onset of MP treatment. The results suggest involvement of CXCL11 and IL-18 in immunopathogenesis of MS.