Cryoglobulinemia may be found in up to 30% of patients that had received liver transplants after hepatitis C virus (HCV) cirrhosis. Three types of cryoglobulinemia are recognized: type I, composed of monoclonal immunoglobulins associated with lymphoproliferative diseases and myeloma; type II cryoglobulinemia are comprised of a monoclonal component which has rheumatoid factor activity and hence binds to polyclonal immunoglobulins (in certain parts of the world have been found to be associated with hepatitis C infection); and type III cryoglobulinemia consist exclusively of polyclonal immunoglobulins with rheumatoid factor activity (associated with connective tissue diseases and chronic infections including hepatitis C). Immunocompentence, autoimmunity and clonal expansion of B cell lymphocytes have not been analysed simultaneously in previous reports of patients with cryoglobulinemia after liver transplantation. We here describe immunological abnormalities associated with cryoglobulinemia in a patient who had received liver transplant for HCV cirrhosis. In addition, in the present work HCV RNA determination was performed directly in the cryocrit and not only in peripheral blood. We have observed enrichment of HCV RNA in the cryoprecipitates which might be a better demostration of the posible rol of HCV in the pathogenesis of the cryoglobulinemia.