The clinico-pathologic findings in an additional case of gliomatosis cerebri are reported: a 60-year-old woman died 8 months after the onset of a progressive deterioration of both the neurologic and mental conditions. Neuropathologic examination disclosed wide demyelination of both hemispheres, communicating through the corpus callosum, extending downward along the internal capsule to the brainstem structures. Cellular stains showed the presence of elongated astrocytes, multinucleated cells, mitotic and anaplastic figures, involving the demyelinated areas and the neighboring regions, and allowed the diagnosis of gliomatosis cerebri diffusa. The nosologic and pathogenetic aspects of this rare entity are discussed.