Although red cell antigens are not thought to contribute to the homograft rejection process. there has been general insistence that human renal homografting should be restrieted to those cases in which the major blood groups are identical in the donor and recipient patients(1–3). Inasmuch as the red cell antigens are widely distributed in human tissues, including the kidney(4)- it has been feared that the mismatched graft would lead to either immediate or delayed red cell agglutination. Recently, we have performed 3 renal transplants in the presence of donor-recipient major blood group incompatibilities. No undesirable sequelae were observed.