By means of monoclonal antibodies against surface antigens of mononuclear cells we examined alterations of T-cell-subpopulations of peripheral blood and liver tissue in the course of acute HBsAg-negative hepatitis. Used methods for determination were the immunofluorescence for blood lymphocytes, respectively the peroxidase-anti-peroxidase-(PAP)-technique for round-cell-infiltrates of the liver based on paraffin fixed sections. The focus of attention was the relation of T4-(helper/inducer) to T8-(suppressor/cytotoxic) cells, the so-called immuno-regulatory quotient. With advancing improvement in the course of the disease we observed in peripheral blood a decrease of T4+/T8+ ratio from very high (3.6) to normal (1.9) values. By examination of the tissue round-cell-infiltrates we found a contrary behaviour to the peripheral blood with a low T4+/T8+ ratio in the liver, characteristic to more acute phases and due to an T8+-cell interchange between periphery and liver. This may be common for all virus diseases and without specificity for defined types of acute hepatitis. Beside this exists the possibility T4+/T8+ ratio has any prognostic value.