The development of spontaneously acquired Factor VIII inhibitors is rare and may lead to serious hemorrhagic sequelae. We report here the case of a patient who acquired a Factor VIII inhibitor two years after an allogeneic bone marrow transplant for CML. This occurred in association with a flare of chronic graft versus host disease (GVDH). He responded to corticosteroid therapy. A review of autoimmune phenomena associated with chronic GVDH and the treatment of Factor VIII inhibitors is discussed.