BACKGROUND: Astrocytoma in spinal cord is rare, comprising only 1% of all primary central nervous system tumors. Malignant astrocytomas( grades III and IV) account for only 7.5% of intramedullary glioma occuring in all age. Dissemination from malignant astrocytoma in spinal cord to the cerebral subarachnoid space has been rarely reported. CASE DESCRIPTION: A 22-year-old male was brought for evaluation of a back pain and progressive left leg weakness over 40 days. MRI of the thoracolumbar spine showed intramedullary mass lesion(T11-L1). Concurrent cranial CT and CSF cytology showed no abnormal findings. The tumor was removed partially. At that time, pathologic diagnosis was low grade astrocytoma. He was given regional irradiation. Six months after surgery the patient was reevaluated because of seizure. CSF cytology revealed malignant cells. Brain MRI showed leptomeningeal carcinomatosis with hydrocephalus. A second pathology of the tumor revealed malignant astrocytoma. CONCLUSION: We report a arae case of spinal intramedullary malignant astrocytoma with intracranial seeding.