A nine-day-old female with cerebellar medulloblastoma treated by surgical and radiation therapy is reported. She suffered from vomiting within a few days after birth. Subsequently, her head became enlarged and she was admitted to our hospital. CT scan on admission showed a large mass lesion at the cerebellum expanding to the pineal portion, and marked hydrocephalus. At the age of 14 days, a ventriculo-peritoneal shunt was carried out, and at the age of 67 days, radical resection of the tumor was performed. The histopathological diagnosis was medulloblastoma. Postoperatively, radiation therapy of the brain was carried out. Irradiated dose was 30 Gy on the whole brain and 20 Gy at the location of the lesion. She was discharged at the age of seven months. She remained in good condition with no neurological deficit except for nystagmus. One week later, it was found that she was unable to move her legs and she was readmitted to our hospital. CT scan showed no remarkable change in the intracranial region, but spinal cord swelling was revealed at the Th12-L5 level. Myelography showed a filling defect at the L3-5 level. Radiation therapy of the spinal cord was performed, and the paraparesis gradually improved. However, her general condition was getting worse, and the following CT scan showed intracranial recurrence of the tumor. She deteriorated day by day and at the age of 9.3 months she expired. Brain tumors during the neonatal period are very rare, especially neonatal medulloblastoma. Only 24 cases can be found in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)