Three cases of olivopontocerebellar atrophy, one of which included a cerebellar biopsy, have been examined for ultrastructural changes. Degenerative changes were identified within the afferent cerebellar fibers and within the cerebellar neurons, especially the Purkinje cells. Although the majority of the degenerative alterations have been previously described in a variety of disease states, there were some findings seen in our material that have not been previously reported, including unusual striped bodies and Lafora body inclusions within Purkinje dendrites. The relationship between OPCA and other diseases is discussed and a possible slow-viral etiology is considered.