White matter degeneration is one of the pathological conditions of dentatorubral-pallidoluysian atrophy. Autopsy brains exhibited a reduced number of glial cells in the lesions and an involvement of oligodendrocytes in nuclear inclusion formation, which previously has been recognized only as a pathological hallmark in neurons. Dentatorubral-pallidoluysian atrophy transgenic mice showed an increased number of affected glias with increasing age and with larger expansions of CAG repeats. These findings suggest that glial cells in dentatorubral-pallidoluysian atrophy also are involved in the polyglutamine pathogenesis.