The objective of this study is to test the effectiveness of the drug amantadine for the treatment of chorea associated with Huntington's disease. Amantadine is an antiviral drug that has been used to treat a variety of illnesses including Parkinson's disease. Amantadine works by attaching to special sites called NMDA (N-methyl-D-aspartate) receptors and blocking the normal activity of glutamate there. Glutamate is an amino acid released by brain cells and has been associated with the symptoms of Parkinson's disease.