Jaundice with evidence of hepatocellular damage of moderate severity was observed in a patient who received methyldopa. The diffuse mononuclear infiltration of the liver tissue was found to consist of 90% E-rosette-forming cells. Peripheral lymphocytes gave a markedly positive macrophage migration inhibition (MlF) test against methyldopa. The number of T lymphocytes in the peripheral blood was at the lower limit of normal but they proved to be functionally inactive, as demonstrated by the results of a local xenogeneic graft-vs-host reaction test. The liver disease was associated with hyperglobulinemia, a decrease of the third and fourth components of complement and the presence of incomplete erythrocytic antibodies, leukoagglutinins, antinuclear factor, and smooth muscle antibody. Follow-up after discontinuation of the drug revealed a gradual return to normal of liver function and MlF tests, normalization of cellular immunity, and disappearance of the humoral antibodies. It is assumed that sensitization by methyldopa triggered the autoaggressive phenomena and their ultimate manifestation in the liver.