Cytopenias following bone marrow transplantation may be severe and life-threatening. These have been described post-allogeneic Klumpp, 1991: Bone Marrow Transplant 8:159-171. or post-autologous bone marrow transplants Khouri et al., 1994: J Clin Oncol 12:748-758. as well as with peripheral blood stem cell transplantation Klumpp et al., 1992: Am J Hematol 41:215-217. It can be immune mediated, associated on occasions with graft-versus-host disease (GVHD) Anasetti et al., 1989: Blood 4:1054-1058; however, in most cases, the underlying mechanism is uncertain. The treatment of post-transplant cytopenias is not well established, and they are often refractory to immunosuppressive therapy with steroids. Herein we describe two cases of neutropenia after allogeneic bone marrow transplantation that improved after therapy with high-dose intravenous immunoglobulin.