Acute myelofibrosis is a rare hematologic disorder characterized by pancytopenia, normal erythrocyte morphology, extensive marrow fibrosis, and a rapidly fatal clinical course. The etiology of this disease is unknown, but the malignant cell may be of megakaryocytic lineage. Although allogeneic bone marrow transplantation may be effective in achieving complete hematologic remission, optimal management of this rare and often rapidly fatal disease remains to be defined.