A 44-year-old man came to our clinic, complaining of slowly progressive disturbance of visual acuity and of ocular movement. This patient suffered from headache, narrowing of visual field and polyuria about 20 years ago, and received surgical and radiation therapy under the diagnosis of pituitary adenoma. Clinical symptoms and signs of this patient, except for bitemporal hemianopsia, almost completely disappeared after these treatment. The detailed information about the histology and radiation dose are not available at the present time. CT scan in our clinic revealed a round low-density area at the suprasellar region and a high density area at the left quadrigeminal cistern. Pineal calcification was compressed to the right about 2-3 mm from midline. This high density mass were not enhanced with contrast medium. Vertebral angiography showed a slight lateral displacement of the left medial posterior choroidal artery. Specimen of tissue removed 20 years ago was reexamined but definitive diagnosis could not be established. Presumptive diagnosis of an ectopic pinealoma in the suprasellar region treated successfully 20 years ago, and its recurrence in the pineal region was made. On May 24, the patient underwent a posterior fossa craniectomy and the pineal region was explored via the infratentorial supracerebellar approach. On sectioning the precentral cerebellar vein, yellowish mass was seen in the quadrigeminal cistern. Aspiration of this mass yielded dark red liquid hematoma. Incising into the capsule, a dark brownish mass of about 4g was removed en bloc.(ABSTRACT TRUNCATED AT 250 WORDS)