A case of multiple myeloma forming an intracranial mass which invaded the skull base was reported. A 72-year-old woman was admitted to the hospital because of left oculomotor paresis. Plain craniograms showed multiple punched out lesions. A CT scan demonstrated a mass lesion, which was homogeneously slightly enhanced with contrast medium, in the middle cranial fossa. MRI, both T1 and T2 weighted images, showed an isodensity mass. In the carotid angiograms the tumor was fed by the right branches of the cavernous portion of the internal carotid artery and the maxillary artery. Laboratory data were as follows: ESR: 132mm/30min, serum TP: 9.0g/dl, IgG: 4670mg/dl, IgA: 430mg/dl, and urinary Bence-Jones protein was detected. Bone marrow biopsy of the illiac bone demonstrated myeloma cells. During hospitalization oculomotor paresis disappeared, and the patient was treated with intramuscular interferon-alpha. Multiple myeloma which invades the skull base is rare, and only 10 cases have been reported since 1977. Moreover, the biclonal type is only 0.5% of all multiple myelomas.