The authors describe two cases of chronic lympocytic leukaemia complicated by pure red cell aplasia of autoimmune origin. The first patient achieved complete recovery of erythropoiesis after short-term immunosuppression by means of cyclophosphamide and prednisone. The second patient did not respond to the same combination of immunosuppressive drugs and remission was achieved by administration of antithymocyte globulin. In the discussion the authors deal with contemporary knowledge of the pathogenesis of autoimmune erythroblastopenia and mechanismus of action of antithymocyte globulin.