Graft-v-host disease (GVHD) is the clinicopathologic syndrome that results from the reaction initiated by a "graft" of immunologically competent lymphocytes introduced into a "host" that confronts the graft with a histocompatibility difference, but is unable to mount an immunologic attack against the donor lymphoid cells. Although GVHD is most commonly recognized as a complication of allogeneic marrow transplantation, GVHD has also been reported following transfusion of nonirradiated blood products to patients with compromised immunologic function. Graft-v-host disease has been described in neonates who received intrauterine or exchange transfusions for hemolytic disease of the newborn,1 in children with congenital immune deficiency or progressive vaccinia necrosum who were given fresh plasma or blood,2 in patients with leukemia or lymphoma who were given granulocyte transfusions,3,4 and in patients with neuroblastoma5 or Hodgkin's disease6 who were given transfusions of packed RBCs only. Typically, a seemingly