Plasmacytoma originating in the cranial bone is a rare disease. A report is presented of a case of plasmacytoma originating in the parieto-occipital region. The patient was a 62-year-old male with palpation of a parieto-occipital mass as chief complaint. He showed no neurological deficit. Ig-G in the serum was 2240 mg/dl, and M-protein (n-type) was demonstrated in the serum. Bence-Jones protein was negative and bone marrow was normal. Skull X-ray showed osteolytic change in the parieto-occipital region. CT scan and MRI demonstrated a markedly enhanced mass extending from the epidural to the subcutaneous space at the parieto-occipital region. Common carotid angiography showed remarkable tumor stain flowing from the occipital artery, the superficial temporal artery, and the middle meningeal artery. Following embolization of the bilateral occipital artery, parieto-occipital horse shoe scalp incision was done. The tumor was elastic soft and bled easily around the margin of destroyed bone. Subtotal removal of the tumor was accomplished. The removed surgical specimen of the tumor was found to be plasmacytoma. The patient's postoperative course was favorable and no neurological deficit was found. Laboratory studies revealed a remarkable reduction of Ig-G in the serum to 1170 mg/dl. Six months after the operation, no signs of recurrence were seen on CT scan. Plasmacytoma originating in the cranial bone is so rare that only 18 cases have been reported to date. In these cases, laboratory studies have shown no evidence of anemia, Bence-Jones protein in urine, and abnormality of the bone marrow which are characteristic of multiple myeloma.(ABSTRACT TRUNCATED AT 250 WORDS)