ABSTRACTBackgroundAlthough it is well established that there is cognitive dysfunction in spinocerebellar ataxia type 3 (SCA3), it is unknown whether cognition deteriorates with disease progression. We therefore prospectively studied cognitive function in patients with SCA3.MethodsEleven patients with SCA3 were assessed using an extensive neuropsychological test battery and retested after 3.5 ± 0.4 years.ResultsIn addition to ataxia and motor control, verbal learning and verbal and figural memory deteriorated significantly during the follow‐up period. An increase in depressive symptoms was not observed.ConclusionsThe observation that memory and learning abilities deteriorated with disease progression suggests that cognitive dysfunction is an integral part of SCA3. Because the applied tests for memory function did not require motor responses, cognitive decline cannot be attributed to progressive cerebellar ataxia. The deterioration of verbal and figural memory can be explained either by extracerebellar pathology or by disruption of cerebellar‐cerebral circuitries. © 2013 International Parkinson and Movement Disorder Society