Spinocerebellar ataxias (SCAs) are a genetically diverse group of dominantly inherited disorders that share clinical features that result from dysfunction and degeneration of the cerebellum and its associated pathways. Although nearly 40 genes are currently recognized to result in SCA, shared mechanisms for disease pathogenesis exist among subsets of the SCAs. The most common SCAs result from a glutamine-encoding CAG repeat in the respective disease genes. This chapter discusses the varied genetic etiology of SCA and attempts to categorize these disorders based on shared mechanisms of disease. We also summarize evaluation and management for the SCAs.