A 44-year-old woman was admitted to our department because of a painless lump on her forehead. Physical examinations were normal except for this lump. Both laboratory data and neurological findings were normal. Plain skull radiograph showed a 4.5 X 5.0 cm honeycombed radiolucent defect in the frontal bone. CT scan demonstrated this lucent defect as a reticular pattern by means of changing the window levels. Moreover, invasive lesion of the inner table which could not be identified in the plain radiographs, was also demonstrated on CT. A left common carotid angiogram showed irregular pooling of contrast material in the radiolucent area of the frontal bone. Angiographically, blood supplies to this tumor were mainly contributed by the frontal branches of the middle meningeal artery and a meningeal branch of the anterior falx artery from the terminal portion of the ophthalmic artery. A bone scintigram revealed accumulation of radioisotope in the lesion. A highly vascular tumor, which was partially adherent to the underlying dura, was removed as en bloc. Postoperative course was uneventful. The histology revealed thin-walled dilated vessels between the trabeculae, and it was diagnosed as cavernous hemangioma of the bone. Hemangioma of the calvarium is estimated to constitute 0.2% of all osseous neoplasms and 10% of primary benign neoplasms the of the skull. Hemangioma of the skull frequently involves the frontal bone. The condition is often found in middle-aged females. The symptom is only a slowly growing, painless lump in most of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)