Inclusion criteria:

• Clinical features of Huntington's disease (HD) and a confirmatory family history of HD and/or a CAG repeat expansion of at least 37
• Stage I, II, or III of illness (TFC greater than or equal to 5)
• Ambulatory and not requiring skilled nursing care
• Patients must use effective birth control
• Concurrent psychotropic medications must be at stable dose for at least 4 weeks prior to study
• WBC count at least 3,800/mm3
• Creatinine no greater than 2.0
• Alanine aminotransferase (ALT) no greater than 2 times upper limit of normal

Exclusion criteria:

• Prior minocycline use within 2 months of baseline visit
• History of known sensitivity or intolerability to minocycline or any other tetracycline
• History of vestibular disease
• Use of any investigational drug within 30 days of baseline visit
• Treatment with any drug that may cause lupus-like symptoms (e.g., procainamide or hydralazine) within 4 weeks of baseline visit
• Pregnant or nursing
• Underlying hematologic, hepatic, or renal disease
• Evidence of unstable medical illness
• Illness that requires use of coumadin
• Unstable psychiatric illness defined as psychosis (hallucinations or delusions), untreated major depression within 90 days of baseline visit, or suicidal ideation
• Substance (alcohol or drug) abuse within 1 year of baseline visit
• History of systemic lupus erythematosis (SLE) or a history of SLE in a first-degree relative
• Positive ANA screening (at or above 1:80)