Chorea-acanthocytosis (CHAC. MIM 200150) is an autosomal recessive neurodegenerative disorder characterized by the gradual onset of hyperkinetic movements and abnormal erythrocyte morphology(1,2) (acanthocytosis). Neurological findings closely resemble those observed in Huntington disease(3-8). We identified a gene in the CHAC critical region(9) and found 16 different mutations in individuals with chorea-acanthocytosis. CHAC encodes an evolutionarily conserved protein that is probably involved in protein sorting.