Spinocerebellar ataxia type 1 (SCA1) is a relatively rare autosomal-dominant neurological disorder. SCA1 has the intriguing feature that the disease-causing mutation is the expansion of an unstable trinucleotide repeat, specifically a CAG repeat that encodes the amino acid glutamine in ataxin-1. During the past 10 years, substantial progress has been made towards understanding the pathogenic mechanism in this disease. The nucleus has been identified as the subcellular site where the mutant protein acts to cause disease. Evidence indicates that expansion of the glutamine tract alters the folding properties of ataxin-1. Finally, several cellular pathways have been identified which are able to impinge on the SCA1 disease process. The characterization of these pathways and their role in SCA1 will guide research over the next several years.