Huntington disease (HD) derives its eponymous title from Dr George Huntington, who described multiple affected individuals in a large North American kindred in 1872. His paper, published in the Philadelphia journal The Medical and Surgical Reporter, gave a graphic description of the progressive neurological disability that has endowed HD with the unenviable reputation of being one of the most feared and unpleasant hereditary disorders in man. The natural history is characterized by slowly progressive selective cell death in the central nervous system, and there is no effective treatment or cure. The prevalence in most parts of the world is approximately 1 : 10,000, although higher in some areas, such as Tasmania and the Lake Maracaibo region of Venezuela. The onset is mostly between 30 and 50 years, but it can start at virtually any age, including a rare juvenile form with different clinical features. The variable age of onset has been explained, at least in part, by the discovery of the underlying molecular defect.