The purpose of this study is to assess the effect of creatine on slowing the worsening of HD symptoms and to assess the safety of creatine in long-term use.

Subjects will participate in sixteen (16) study visits and eighteen (18) telephone contacts over three years.

Eligible subjects will receive either up to 40 grams powdered creatine monohydrate per day or matching placebo for a total of 36 months.

• Drug: Creatine Monohydrate (HD-02)
• Drug: placebo

• Active Comparator: Eligible subjects randomized into this arm will receive up to 40 grams powdered creatine monohydrate per day for a total of 36 months
• Placebo Comparator: Eligible subjects randomized into this arm will receive up to 40 grams of placebo per day for a total of 36 months

Inclusion Criteria:

• Male or female age 18 or older.
• Subjects must have clinical features of HD and a confirmatory family history of HD; OR CAG repeat expansion greater or equal to 36.
• Subjects in Stage I or II of illness (TFC greater or equal to 7).
• Subjects must be ambulatory and not requiring skilled nursing care at the time of enrollment.
• Women of childbearing potential (i.e., those not postmenopausal or surgically sterile) must have a negative pregnancy test, be non-lactating and use adequate contraception methods during the study. Adequate birth control includes: abstinence; oral, implanted or injected contraceptives, e.g., birth control pills; intra-uterine device; barrier (e.g., vaginal ring or diaphragm/cervical cap with spermicide; transdermal patch and/or partner vasectomy). Reliable contraception must have been in use 30 days prior to the Baseline Visit.
• Subjects currently taking psychotropic medications (including anti-depressants and neuroleptics) must be on stable dosages for at least 30 days prior to randomization.
• Subjects must be capable of providing informed consent and complying with trial procedures.
• Subjects must be able to take oral medication.

Exclusion Criteria:

• History of known sensitivity or intolerability to creatine monohydrate.
• Exposure to any investigational drug within 30 days of randomization (Baseline visit).
• Use of supplemental creatine at a dose greater than 10 grams within 90 days of randomization (Baseline visit).
• Use of supplemental Coenzyme Q10 at a dose greater than 600 milligrams daily within 90 days of randomization (Baseline visit). CoQ10 supplements totaling greater than 300mg daily are not allowed during the study but may be taken prior to the baseline visit.
• Screening creatinine greater than 2.0 mg/dL.
• Screening white blood cell count less than 3800/mm3.
• Screening alanine aminotransferase greater than 2 times the upper limit of normal.
• Screening laboratory abnormalities that in the judgment of the investigator would jeopardize safe conduct of study.
• Current or history of substance (alcohol or drug) abuse within one year of randomization (Baseline visit).
• Clinical evidence of unstable medical illness in the investigator's judgment.
• Clinical evidence of unstable psychiatric illness defined as psychosis (hallucinations or delusions), untreated major depression or suicidal ideation within 90 days of the Baseline visit.

Additional Exclusion Criteria for Imaging Sites:

• Previously obtained MRI scans with evidence of infection, infarction or other focal lesions.
• Presence of pacemakers, aneurysm clips, artificial heart valves, ear implants, metal fragments or foreign objects in the eyes, skin or body or any other known contra-indication to MRI.