An 82-year-old woman was admitted to the Department of Neurosurgery, Saiseikai Fukuoka General Hospital with complaints of persistent headache and left hemiparesis. Neurological examination on admission revealed mild left hemiparesis with hyperreflexia. However, no choked disc nor pathological reflexes were noted. Roentgenograms of the skull showed thickening of the bone in the right temporoparietal region with intracranial calcification. CT showed a large right frontoparietal mixed dense space-occupying lesion bordered by a high dense calcified rim. The right lateral ventricle was compressed while the left exhibited a deviation to the left. Furthermore, thickening of the right frontal and parietal bone around the margin of mass was noted. The patient was operated upon under the diagnosis of calcified chronic subdural hematoma. A large osteoplastic flap was turned down on the right front parietal area and hypertrophy of the skull, especially around the hematoma, was noticed. Over the dura just beneath the hypertrophic lesion of the calvaria, a soft, reddish granulation tissue was noted. The dura was stripped easily from the outer membrane. The capsule was opened and the content was found to be of compact consistency, screeching when cut, and it appeared to be filled with large clots, not all homogeneously organized and made out of a substance composed of reddish-yellow material. The inner membrane was removed except for the frontal lesion where remarkable adhesion to the arachnoid membrane was noted. The postoperative course was uneventful. At the time of the patient's dismissal, her symptoms had completely disappeared. Histologically, the granulation tissue to be the bone marrow consisted of three hematopoietic cells.(ABSTRACT TRUNCATED AT 250 WORDS)