A case of pleomorphic xanthoastrocytoma, the first case in Japan, is reported. This is a 25-year-old woman with a history of convulsive seizures which were initiated on her left arm 13 years prior to admission, On admission, physical and neurological examinations revealed no abnormalities. CT-scan disclosed a large well-defined low density area in the right fronto-temporal region. A small peripheral portion of the low density area was enhanced by contrast media. The high density area located immediately beneath the inner table of the skull. Right carotid angiogram showed a large avascular area corresponding to the cystic lesion. At the operation, there was a mural nodule in the frontal cortex involving the leptomeninges. The tumor was relatively soft and was milky-white in color. Under this tumor was a large cyst containing xanthochromic fluid. The mural nodule was totally removed and the cyst was widely opened. Postoperative course was uneventful and she received a radiation therapy (5500 rads). She was discharged without any neurological deficits. Histologically, the tumor was highly cellular. The tumor cells were markedly pleomorphic showing bizarre giant cells and multinucleated cells. However, tumor necroses and mitotic figures were absent. With immunoperoxidase method and PTAH stain, these tumor cells were confirmed to be astrocytic. In some areas, tumor cells were surrounded by reticulin fibers. Many tumor vessels presented marked hyalinous degeneration. By electron microscopy, many tumor cells contained lipid droplets. This case was considered to be pleomorphic xanthoastrocytoma (Kepes). Pleomorphic xanthoastrocytoma was designated by Kepes et al in 1979 as a new tumor entity. They described clinical and pathological characteristics of this tumor as follows. The age of the patients were young and the tumors were frequently cystic. The tumors were superficially located in the brain and involved the leptomeninges. Despite marked nuclear pleomorphism, mitotic figures of the tumor cells or necroses were rare. In contrast to their pleomorphic cytology, the biological behavior of this tumor appeared to be favorable. The authors stressed the clinical and pathological significance of this tumor. Because, this is the tumor with malignant appearance in light microscopy, but with favorable prognosis.