AB0-incompatible kidney transplantation involves major risk of early acute vascular rejection. We report for the first time the successful preparation for renal homografting of a recipient of an HLA-haplotype identical, AB0 blood group B-incompatible renal homograft from a living related donor by immunoadsorption for removal of B blood group antibodies at days -4, -2 and -1. The iso-agglutinin anti-B titer was 1:256 before and 1:8 after three adsorption sessions in extracorporeal circuit. Before and after transplantation the splenectomized recipient was given azathioprine, prednisone and cyclosporine A. After homografting the anti-B iso-agglutinin and the anti-B isoimmune titers were mostly below 1:8 and never exceeded 1:32 and 1:64 respectively. 111 days after transplantation the recipient had a creatinine concentration in plasma of 160-180 mumol/l and was free of infectious complications. Thus the introduction of specific and convenient immunoadsorption of blood group antibodies by pheresis for preparation of renal homograft recipients may in future extend the indications for kidney transplantation in AB0-incompatible subjects, who have so far been denied the benefit of a living renal homograft.