We will examine three subject groups in this study: those with mild HD, those with moderate HD, and normal controls. Fifteen subjects will be examined in each group, for an overall total of forty-five subjects. HD subjects will be recruited from the UCLA Huntington Disease Center of Excellence where they have been followed with serial neurologic examinations and completion of all portions of the UHDRS every 6-12 months. Subjects that have been given a diagnosis of HD based on appropriate motor signs and a confirmatory genetic test or a known family history of HD will be invited to participate. Healthy control subjects will be recruited from the clinic as well through spouses or other unaffected relatives of patients. In addition, control subject data acquired from previous studies will be used after matching for age. All subjects will be over the age of 21 and free of other medical illnesses that could also affect brain function and will be able to give informed consent. Mild HD is defined as having Total Functional Capacity [TFC] scores on the UHDRS of 11-13, moderate is defined as TFC of 7-10, and normal control subjects will be free of any neurologic or psychiatric illness. Subjects will be free of antipsychotic or antidepressant medications, benzodiazepines, or other medications known to affect central nervous system function for at least 10 days prior to QEEG examination.