Spinocerebellar ataxia type 6 (SCA6) is an autosomal dominant cerebellar ataxia caused by a CAG repeat expansion in the human alpha1A-calcium channel gene. In this section, recent advances regarding pathogenic mechanism underlying in SCA6 is presented. When human alpha1A-calcium channel gene with expanded CAG repeat is transfected into HEK cells, the voltage dependence of inactivation shifting negatively 6 to 11 mV was observed, indicating that calcium influx across plasma membrane is reduced. When alpha1A-calcium channel protein and polyglutamine stretch are examined in SCA6 brain by immunohistochemistry, formations of aggregations within the cytoplasm of SCA6 Purkinje cells were seen. These findings may indicate that both alteration of calcium channel function and formation of protein aggregation are involved in the pathogenic mechanism of SCA6.