A 47-year-old patient with blood group O inadvertently received a mismatched kidney from a donor of blood group A. Two days after transplantation, the clinical, biochemical manifestation of an intrarenal, intravascular coagulation was seen. This was treated by plasma exchange with the rapid reversal of all parameters, and reduction of both the IgG and IgM component of the circulating anti-A antibody. The patient, 20 months after transplantation, has normal renal function. Subsequent repeated biopsies have shown no recurrence or manifestation of the effects of the intravascular coagulopathy.This case report documents, for the first time, the reversal of the known deleterious effects of major blood group incompatibility on renal transplantation by the use of a new technique, modified plasmapheresis. Furthermore, it implies that the limitation of transplantation of kidneys on the basis of major ABO blood groups may not be justifiable in all instances.