Patients with HD and their family members will be recruited from specialty clinics (Human Genetics, Neurology, Psychiatry) that advise and treat people affected by HD. In addition, in some areas community clinics and neurologists who see HD patients will recruit participants for this study.Participants may also receive information about the study through a website, clinical practices, support groups, advocacy newsletters, etc. and place a direct request to be considered for participation in the study. Community controls will be identified, using advertisements, flyers and newsletters, by study site staff with the support of the Enroll-HD operational staff.