A 52-year old man had a generalized seizure followed by progressive memory disturbances, affective changes, right hemiplegia and aphasia. He died 4 years later after a period of coma. Neuropathological findings included slight cortical atrophy, pallor of the centrum ovale, and infiltration of the cortex and subcortical white matter by neoplastic glial cells, with neither major neuronal loss nor spongiosis. Microglial rod cells were observed. The gliomatosis extended within the thalamus and subthalamic area on both sides, whereas the brain stem was much less involved. The spinal cord and peripheral nerves were not examined. Abnormal glial cells were stained by the glial fibrillary acid protein, which confirms the astrocytic differentiation of the tumoral cells.