Multiple sclerosis (MS) is an autoimmune disease in whose pathogenesis Th1 cells play an important role. It has recently become clear that interferon beta-1b (IFN beta-1b) treatment is effective in ameliorating relapsing-remitting multiple sclerosis (RRMS). The treatment efficacy of IFN beta-1b for multiple sclerosis is potentially attributable to the immune regulatory properties of the drugs. In the present study, we compared the expression of Th1-related CXCR3/CCR5 chemokine receptors and Th2-related CCR4/CCR3 chemokine receptors on T cells derived from MS patients and those derived from healthy controls. Also, we have investigated the chemokine receptor expressions in MS patients undergoing IFN beta-1b therapy. The expression of these Th1/Th2-related chemokine receptors were assessed at the baseline and longitudinally over a period of 12 months after the start of treatment in 10 RRMS patients grouped as responders and nonresponders according to their clinical response to IFN beta-1b therapy. The percentage of CXCR3-expressing CD4⁺ T cells in patients with MS was significantly elevated compared with those of healthy controls. Moreover, MS patients in an active phase showed an increased CD4⁺CXCR3⁺/CD4⁺CCR4⁺ ratio in relation to patients in  a  remission  phase.      The  increased   percentage of   CD4⁺CXCR3⁺    cells    in    blood   was   associated with relapses of MS. At 12th months after the treatment, the CD4⁺CXCR3⁺/CD4⁺CCR4⁺ ratios were significantly lower in both responders and nonresponders. This study suggested that the CD4⁺CXCR3⁺/CD4⁺CCR4⁺ ratio, representing Th1/Th2 balance, would be a marker of immunological activity in MS patients, and that IFN beta-1b can correct the Th1/Th2 imbalance.