Background: Nonprogressive cerebellar ataxias are characterized by a persistent, nonprogressive ataxia associated with cognitive impairment. Cerebellar hypoplasia on imaging is variable but is not predictive of the degree of ataxia or cognitive impairment. Objective: To describe a family with a nonprogressive cerebellar ataxia associated with cognitive and motor impairments that improve with age. Design: Genetic study in a family with nonprogressive cerebellar ataxia. Clinical and imaging features are also described. Setting: Community hospital. Patients: Both parents and 3 children from an affected family. Main Outcome Measures: Clinical features, magnetic resonance imaging findings, and genetic findings. Results: A genome-wide single nucleotide polymorphism screen did not show clear linkage to known spinocerebellar ataxia loci, in particular spinocerebellar ataxia type 15. Repeat spinocerebellar ataxia loci expansions were excluded. Magnetic resonance images of all affected individuals demonstrated cerebellar vermian abnormalities. Conclusions: These findings suggest that nonprogressive cerebellar ataxia is genetically heterogeneous and, when associated with gradual improvement in cognition and motor skills, likely represents a separate, distinct clinical entity.