The evidence that cell mediated immunological reactions may contribute to the development of Chronic Active Hepatitis (CAH) and Primary Biliary Cirrhosis (PBC) suggests the use of immunosuppressive agents in these disorders. To study the cellular immunity and the response to immunosuppressive therapy in chronic liver disease, the Rosette Inhibition Test (RIT) was employed. This test was applied to evaluate the degree of T lymphocytes sensitization in autoimmune diseases. 53 patients with chronic liver disease were examined: PBC (9), CAH (30) and Chronic persistent Hepatitis (CPH) (13); 14 of these subjects had repeated controls of the RIT during the treatment with cortisone and/or azathioprine. The concentration of antilymphocyte serum causing 25% rosette inhibition relative to control was taken as the end point (MIC = minimal inhibitors concentration). In 22 healthy subjects the range of MIC was 1/14000 to 1/32000; the MIC in patients with CPH fell into the same range. In 80% of CAH and in 77% of PBC the MIC was higher than normal controls, showing a T lymphocytes sensitization. In patients subjected to immunosuppressive therapy the MIC usually changed towards the normal values and in 8 cases became normal after some months of treatment