A 38 year old patient developed multiple cranial nerve palsy, seizures and progressive alteration in consciousness. CSF examination revealed tumor cells and a tentative diagnosis of leptomeningeal carcinomatosis from an unknown primary tumor was made. Treatment with intrathecal methotrexate and cranial radiation therapy was started without effect. At autopsy widespread leptomeningeal gliomatosis originating from a previously unknown astrocytoma of the hippocampus was found.