Huntington's Disease (HD) is a neurological, familial disease, passed from parent to child through a mutation on the 4th chromosome. Each child of an HD parent has a 50-50 chance of inheriting the gene which causes degeneration of brain cells, resulting in the loss of the ability to walk, think, talk, reason, and swallow. Onset generally appears at midlife, but in some, onset occurs in childhood (juvenile HD) or in old age (late onset). The disease profoundly affects the lives of entire families, as the person with HD becomes totally dependent on others for his/her care. About one in 10,000 Americans have this disease. Since 1993, a genetic test has been available to those at-risk, to determine whether or not (s)he carries the HD gene. The test does not indicate at what age the disease will develop.