Gallyas-positive, tau-negative oligodendroglial cytoplasmic inclusions are specific for multiple system atrophy, while both Gallyas- and tau-positive glial fibrillary tangles are a common feature of tau-related neurological disorders. We examined the midbrain of Parkinson's disease (PD) patients and found significant numbers of Gallyas-positive glial inclusions in 17 of the 20 cases. They were most frequent in the dorsomedial part of the substantia nigra. Immunocytochemically, the glial inclusions were negative for tau and tubulin. Glial fibrillary acidic protein immunoreactivity was present in inclusion-containing cells. No such inclusions were observed in Alzheimer's disease (AD) or aged controls. These findings indicate that the glial inclusions present in the PD midbrain are different from those reported previously and unrelated to brain aging or the concurrence of AD lesions.