It is well known that the case of multiple myeloma shows punched-out lesions of the cranium without intracranial hypertension. In this paper a case of multiple myeloma is reported showing intracranial hypertension due to a large tumor that developed in the left parietal bone. There are only 13 case reports about cranial mass lesion of multiple myeloma since 1928. A 52 year-old female was admitted to Iwate Prefectural Isawa Hospital suffering from headache, nausea and vomiting. She had been already diagnosed as multiple myeloma and treated with chemotherapy using Cyclophosphamide, Melphalan and Prednisolone for 2 years. On admission, a large subcutaneous mass was presented on the left parietal region. Craniogram revealed large osteolytic lesion of the left parietal bone and 3 punched-out lesions of the frontal bone. CT scan revealed a large mass lesion in the left epidural space, diploe and subcutaneous space. Angiography showed avascular area. Brain scintigram showed diffuse hot area. Other skeletal bones showed no abnormality. Laboratory examination revealed high concentration of gamma-globulin and high erythrocyte sedimentation rate. Electrophoresis showed high value of immunoglobulin G; immunoglobulin assay was as follows: IgG-6000 mg/dl, IgA-150 mg/dl, IgM-410 mg/dl, IgE-0 mg/dl. Serum electrolytes were within normal limits. Urine didn't include Bence-Jones protein. The patient was diagnosed as multiple myeloma suffering from intracranial hypertension caused by large tumor which developed in the left parietal bone. On the operation, large tumor was existed in the epidural and subcutaneous space invading into the diploe but without infiltration into the dura mater or cerebral cortex.(ABSTRACT TRUNCATED AT 250 WORDS)