• Gliomas that arise primarily in the leptomeninges are rare. Of the 15 reported cases of primary leptomeningeal glioma, only two diffusely involved the leptomeninges. We report the third case of primary leptomeningeal gliomatosis, this in a 55-year-old man who died three months after the onset of symptoms. The clinical manifestations, CSF findings, and the gross appearance of the brain resembled meningitis rather than neoplasm. Results of cytologic examinations of the CSF were normal and the diagnosis was made at necropsy. The diffuse form of primary leptomeningeal glioma has a shorter clinical course and poorer prognosis than the solitary form. Primary leptomeningeal gliomas are believed to arise from heterotopic neuroglial tissue in the leptomeninges.