The DOMINO study is a randomized, double-blind, multi-center, futility study of minocycline in patients with HD. Subjects will be randomized (3:1) to one of the two study arms: (1) the group that receives active minocycline (100 mg po b.i.d.), and (2) the group that receives placebo. Subjects will be enrolled over an approximate six-month period and remain on blinded study drug for 18 months. The primary analysis will involve a comparison of the change over time in TFC between the minocycline group and a fixed value determined from historical control data. A placebo group will also be included to facilitate blinding and to permit a descriptive assessment of the validity of the assumed change over time in historical controls.