Huntington's disease, chorea or disorder (HD) is an incurable neurodegenerative genetic disorder, which affects muscle co-ordination and some cognitive functions, typically becoming noticeable in middle age. It is the most common genetic cause of abnormal involuntary writhing movements called chorea and is much more common in people of Western European descent than in those from Asia or Africa. The disease is caused by a dominant mutation on either of the two copies of a gene called Huntington. This book gathers and presents current research in the study of Huntington's Disease including the outlining effects of mutant htt in the nucleus and cytoplasm and the role of cell-cell interactions in Huntington's Disease pathology, as well as a review of the role of Huntington (HTT) interacting proteins.