It appears that a wide range of antibodies must be taken into account among future recipients of renal allografts. On one hand, the hazard of hyperacute rejection induced by warm allo-antibodies directed against donor's HLA-A, B antigens is well known. It is probable that warm allo-antibodies directed against donor's Ia (HLA-DR) antigens are also harmful. On the other hand, anti-T or B lymphocytes cold auto-antibodies appear neutral, whereas some studies suggest the possibility of enhancing antibodies which may be anti-idiotypic antibodies.