A patient with severe aplastic anemia underwent bone marrow transplantation from her HLA identical sister after a prolonged transfusion history and clinical evidence of shortened red cell and platelet survival. Following the transplant, she exhibited minimal graft vs. host disease which resolved, and was discharged with normal blood counts. Because of falling hemoglobulin, platelets and white blood cell counts 8 weeks following the transplant, graft rejection was suspected. High dose steroid therapy apparently had no effect, since the hematologic parameters continued to fall. She underwent two plasma exchanges, after which all hematologic parameters returned to normal, and she continues to exhibit normal parameters seven months after the transplant. Although other explanations for the reversal of the apparent graft rejection can be considered, the case is presented to call attention to the possibility that plasma exchange, by possibly removing circulating inhibitors of bone marrow function, may be useful and simple method for dealing with graft rejection.