Autoreactive lymphocytotoxic antibodies, which have been found in sensitised dialysis patients, are generally not considered to be harmful to a renal allograft. In this work the presence of such autoreactive antibodies was investigated in the following groups of sensitised endstage renal disease patients: (a) dialysis patients waiting for a first kidney transplant, (b) kidney transplanted patients, and (c) dialysis patients with a previous failed graft. Only sera from the above patients which showed high reactivity (greater than 30%) against peripheral blood lymphocytes of a random cell panel (R-PBL), were screened for the presence of autoreactive lymphocytotoxic antibodies, by testing at different temperatures against autologous T lymphoblasts (PHA-ATL) and EBV-induced autologous B lymphoblasts (EBV-ABL). The results showed that both blood transfusions, and viral infections such as cytomegalovirus (CMV), correlated with the presence of autoreactive antibodies, and that in addition, by using PHA-ATL and/or EBV-ABL as absorbing reagents, it was possible to remove the antibodies. These absorption procedures allowed the identification of the presence of autoreactive antibodies alone or in combination with other alloantibodies.