Spinocerebellar ataxia type 31 (SCA31) is an autosomal dominant form of pure cerebellar ataxia that is caused by a disease-specific insertion containing penta-nucleotide repeats (TGGAA)n . Neuropathologically, cerebellar Purkinje cells are preferentially affected and reduced in number in SCA31, and they are often surrounded by halo-like amorphous materials. In the present study, we performed neuropathological analyses on two SCA31 brains, and discussed the serial morphological changes of Purkinje cells in SCA31.We found that bent, elongated, often folded nuclei were observed frequently in degenerating Purkinje cells with the halo-like structure. Conversely, Purkinje cells without this structure developed marked atrophy with severely slender and condensed nuclei. On the basis of these pathological findings, we propose two different processes for Purkinje cell degeneration in SCA31, namely, shrinkage of Purkinje cells with or without the halo-like amorphous materials. The former, but not the latter, was considered to be specific to SCA31. Correspondingly, fragmentation of the Golgi apparatus was observed more frequently in Purkinje cells with the halo-like structure than in those without this structure. We consider that the profound nuclear deformity and fragmentation of the Golgi apparatus are closely linked with the formation of the halo-like structure in SCA31.