We studied the percentage of double positive (CD4+CD8+) form of T-cells in a group (total 77) multiple sclerosis (MS) patients, measured by means of monoclonal antibodies anti-CD3, CD4/FITC, CD8/RPE and flow cytometry FACScan (Becton Dickinson). In our study we have shown that the percentage of the double positive T cells is higher (p < 0.05) in the peripheral blood of patients with acute exacerbation of MS (n = 21), and in the course of chronic progressive MS (n = 27) comparing to MS remission (n = 29) and other neurological diseases (n = 25) groups. In the study we have shown that the percentage of double positive T-cells in peripheral blood depends mainly on disease activity.