Spinocerebellar ataxia type 31 (SCA31) is characterized by a late-onset slowly progressive cerebellar ataxia, caused by a penta-nucleotide expansion containing (TGGAA)n in an intron of BEAN1 (Am J Hum Genet 2009; 85: 544-57). This disease is common SCA in Japanese, while it is not found in other ethnicity. As clinical trials against SCAs are expected in future, it became essential for us to understand progression rates as well as biomarkers in SCA31. Previous studies reported that an annual progression rate of SCA31 in the Scale for the Assessment and Rating of Ataxia (SARA) score was 0.8 ± 0.1 points (Cerebellum 2017; 16: 518-24). However, detailed clinical parameters are needed to address efficacies of therapies.