A patient presented with myelopathy due to intramedullary thoracic spinal cord glioblastoma 10 months after treatment for a supratentorial glioblastoma. There was no supratentorial recurrence, and no evidence of gross leptomeningeal dissemination documented by CSF cytology, complete myelography, and MR1 imaging. Gross examination of the spinal cord and arachnoid at the time of exploratory thoracic spinal surgery was normal. However, histological review of thoracic arachnoid demonstrated microscopic deposits of glial fibrillary acidic protein (GFAP) positive tumour consistent with malignant astrocytoma. Intramedullary spinal cord metastasis of cerebral glioblastoma rarely occurs, but may develop in association with leptomeningeal tumour dissemination. As local control of primary tumours improves, distant metastasis is likely to become a more common clinical problem. Leptomeningeal gliomato-sis may be very difficult to document, even when clinically suspected and GFAP staining of a biopsy of arachnoid tissue can play an important role in confirming the diagnosis. This information can be critical to establish prognosis and develop an appropriate treatment strategy.