This study is an open-label assessment of behavioral symptoms including depression, impulsivity, and suicidal ideations in patients prior to, and after, taking a stable dose of TBZ for Huntington's disease. All subjects will be evaluated with tests of depression (Beck Depression Scale), impulsivity (QUIP, BIS-11, and computerized impulsivity scales), and suicidal ideation (Columbia Suicide Scale) as a safety measure before they actually start taking TBZ. Since there is a significant lack of awareness of emotional and cognitive symptoms (anosagnosia) in patients with HD, collateral sources will be asked to fill out similar questionnaires based on their knowledge and observation of the patient. Patients and collaterals will be asked to return to the clinic for an identical evaluation plus adverse events, after they have been on a stable dose of TBZ for 4 weeks, which would be 8 ± 1 week after initiating TBZ. Patients will be titrated over 3-5 weeks to best dose as determined by the investigator, up to a maximum of 75 mg/day. As patients are titrating, there will be several telephone contacts conducted. The initial dose will be 12.5 mg BID. Best dose will be largely determined by adverse events and subjective efficacy. Determination of best dose will include two scheduled phone calls and others as needed. Other medications will remain stable between visits.