Two cases of a solitary plasmacytoma of the spine were reported. Case 1, a 59-year-old male, presented with progressive quadriparesis. MRI and myelogram revealed an osteolytic lesion extending from the 5th to the 7th cervical vertebral bodies with extradural mass. Biopsy was made and histologically the lesion was shown to be a plasmacytoma. A halo vest was put on the patient, who received radiotherapy followed by posterior cervical stabilization with autologous ribs and titanium wires. Physiotherapy was continued for a few months until quadriparesis improved remarkably and he was discharged able to walk by himself. Five years later, he is leading a normal daily life without recurrence. Case 2, a 56-year-old male, became paraplegic within a couple of days following chest pain. CT and MRI revealed the destruction of the 5th thoracic spine with cord compression. Emergency laminectomy was performed to decompress the cord and the lesion was diagnosed pathologically as plasmacytoma. Postoperatively both legs were able to move well. The patient received radiotherapy while still confined to bed. Afterwards, following preoperative embolization, transthoracic anterolateral stabilization with autologous rib and instrumentation (Kaneda's device) was carried out. Postoperative chemotherapy was received during the period of physiotherapy. As a result of those treatments, he was enabled to walk by himself with the help of a cane. After discharge, however, he was readmitted and died of metastatic lung cancer originating from the kidney about a year after the onset. Generally speaking, plasmacytoma is malignant. However, its prognosis might be less poor, if solitary. Also it is radiosensitive as was shown in our cases. On the other hand, it can be said that this tumor is the early stage of multiple myeloma. Therefore, in conclusion, solitary plasmacytoma of the spine should be thoroughly treated with tumor resection and stabilization by the anterior and/or posterior approach, and with adjunctive therapy including pre- or postoperative irradiation and chemotherapy.