Sixty eight patients with verified multiple sclerosis (MS) (mean EDSS score 3.1 +/- 1.0) and 50 healthy donors have been investigated. Thirty five patients had relapsing-remitting, 25--secondary progressive, 8--primary progressive course. The remission was in 38, decompensation--in 20, relapse--in 10 patients. Lymphocyte subpopulations were investigated using monoclonal antibodies (Moscow) to the following antigens: CD3 (T-lymphocytes), CD4 (T-helpers), CD8 (T-supressors), CD20 (8-lymphocytes), CD25 (IL-2 receptor), CD16 (natural killers), CD95 (activated cells ready to apoptosis). Cytokines and tumor necrosis factor-alpha (TNF-alpha) levels were measured using ELISA test. HLA antigens were investigated by standard lymphocytotoxic test. In MS we found a fall of CD3, CD4, CD8, CD20 and CD16, but an increase of CD4/CD8, CD95, CD25. The CD95 level correlated with CD4, CD4/CD8 and CD16. In MS spontaneous IL-2, IL-6, IL-8 and TNF-alpha production was raised and stimulated IL-6 and IL-8 secretion was reduced. IL-4, IL-6, IL-8, TNF-alpha and IL-1 beta serum production in vivo was elevated. We found an increase of CD3, CD4, CD16, CD25, but a decrease of IL-1 (p < 0.01) spontaneous production and IL-6, IL-8, TNF-a stimulated secretion in DR2(+) MS patients, comparing to DR2(-) patients and controls. In DR2(-) patients as compared to DR2(+) patients and controls, all lymphocyte subpopulations levels, especially CD8 (p < 0.001) one, were decreased, but spontaneous IL-8 (p < 0.01) production was increased. The data obtained indicate lymphocyte apoptosis activation, targeting promoted lymphocyte destruction, and suggest T helper type-1 reaction prevalence in MS.