Experiments on CBAxC57BL mice with experimental hepatitis induced by carbon tetrachloride showed that transplantation of cells from lymphoid organs of healthy donors stimulates repair processes in the recipients' pathologically changed liver. Normalization was most marked in the liver of animals receiving thymus cells only, which suggests that a deficiency of these cells is present in experimental toxic hepatitis and that the thymus plays a definite role in repair processes in the damaged liver.