A twenty-four-year-old woman presented with asthenia, anorexia and weight los associated with headache, neck ache, lumbo-sacral pain, flaccid quadriparous, bilaterally diminished vision and sphincter disorders. On computerized axial tomography of the skull, only slight signs of ventricular dilatation were seen. Cytochemical study of the cerebro-spinal fluid showed a marked increase in protein and there was a raised erythrocyte sedimentation rate. The patient was treated with steroids in view of the possibility of vasculitis or a demyelinating disorder. However the disease worsened and she died four months after onset of the disorder. Neuro-pathological study showed tumour infiltration of the leptomeninges of the base of both cerebral hemispheres, cerebellum and spinal medulla. The optic nerves, chiasma and spinal nerve roots were also infiltrated with neoplastic cells. No intraparenchymatous tumour was found. The neuropathological findings were compatible with primary diffuse leptomeningeal gliomatosis.