Chorea can have many causes, some hereditary and many sporadic in nature. The archetypal hereditary cause of chorea is Huntington's disease (HD). However, this condition often manifests as a mixed movement disorder, and some individuals with the Westphal variant may not display chorea at all. Moreover, since gene-specific testing has become available, we now know that in many cases of HD, particularly those with late onset, a positive family history may be lacking. In addition, dentatorubro-pallidoluysian atrophy (DRPLA), another dominantly inherited CAG repeat disease, can produce a similar clinical picture. In both conditions, the phenotype may vary according to repeat length, and anticipation and excess of paternal inheritance in younger-onset cases with longer repeat lengths are seen. Neuroacanthocytosis is probably genetically heterogenous, and many instances of "benign hereditary chorea" have been caused by other conditions. If it exists at all, this disorder is exceedingly rare. The principal causes of sporadic chorea include drugs, pregnancy, vascular disease, thyrotoxicosis, systemic lupus erythematosus (SLE) and the lupus anticoagulant syndrome, polycythaemia rubra vera, AIDS and both initial and recurrent Sydenham's chorea. The symptomatic treatment of chorea is unsatisfactory and, at least in HD, neuropsychiatric disturbance may be much more important for the family. Potential disease-modifying treatments such as anti-excitotoxins, antioxidants, free radical scavengers and neuronal grafting are now being explored in this condition.