Argyrophilic cytoplasmic inclusions of oligodendrocytes have been described in cases of multiple system atrophy (olivopontocerebellar atrophy, striatonigral degeneration, and Shy-Drager syndrome). The oligodendroglial cytoplasmic inclusions are immunolabeled with antiubiquitin antibodies. Ultrastructurally, they appear as granule-associated filaments. They have not been found in other neurological diseases or in normal brains, and are now considered to be early and specific markers of multiple system atrophy. More recently, similar argyrophilic inclusion bodies Have Been report in the cytoplasm of neurons and in both oligodendroglial and neuronal nuclei of multiple system atrophy brains. Neuronal and oligodendroglial cytoplasmic inclusions have identical ultrastructural characteristics, but different antigenic properties. The chemical nature of the inclusions is presently unknown and their significance remains controversial: they could be a primary event in the course of the degenerative process or merely an epiphenomenon of some disordered cytoskeletal metabolism.