Isolated granulocytic sarcoma (GS) has rarely been reported in a patient who underwent allogeneic bone marrow transplantation (BMT) for chronic myelogenous leukemia (CML). We report here a patient who developed an isolated GS after achieving hematologic and cytogenetic remission by donor lymphocyte infusion for the relapse of CML following BMT. The size of GS was slightly decreased after local irradiation of 1,500 cGy without further systemic chemotherapy or immunotherapy. He remained in hematologic and cytogenetic remission without systemic relapse of CML for 8 months. Thereafter, he died of sepsis. The appropriate treatment of GS and impact of its occurrence on prognosis following allogeneic BMT has yet to be determined.