Forty patients with multiple sclerosis of a differing course, duration and severity were treated in this series. T-activin was employed as an immunocorrective agent (AFT-6 fraction). The immunological status was assessed in all patients observed prior to, during and after the treatment. Good clinical response was noted in patients with a secondary progressive course; the effect of a short course of treatment with T-activin on the state of patients with a prolonged progressive course or at the stage of stabilization in the presence of severe organic symptomatology was less prominent. AFT-6 showed a beneficial effect on the immunological status of patients, largely on the T-immunity system. Following the treatment, most patients displayed the normalization of the total lymphocyte count and of the proportional content of T-cells with their activity rising.