A 73-year-old man was admitted because of back pain and paralysis of the lower extremities. Magnetic resonance imaging of the spine at the Th4-6 level, obtained after gadolinium injection, demonstrated abnormal signal intensity within the Th5-6 vertebral bodies and an extradural soft-tissue mass on the right posterior side of the spinal canal, compressing the thecal sac. The patient underwent prompt decompression with laminectomy, but this was unsuccessful. A biopsy sample of the mass revealed the histological features of granulocytic sarcoma, including diffuse infiltration of numerous cells containing cytoplasmic granules and immunohistochemical positivity for myeloperoxidase. Two months later, a subcutaneous soft-tissue mass appeared at the anterior chest wall, and this was confirmed to be granulocytic sarcoma by microscopic examination. Both of these tumors were radiosensitive, but the patient died of septic shock. Granulocytic sarcoma usually occurs in association with leukemia or other myeloproliferative disorders. However, it is rarely found before leukemia becomes evident in the peripheral blood or bone marrow; only eight such instances have been reported previously.