In 1872, the American physician George Huntington wrote about an illness that he called "an heirloom from generations away back in the dim past." He was not the first to describe the disorder, which has been traced back to the Middle Ages at least. One of its earliest names was chorea,* which, as in "choreography," is the Greek word for dance. The term chorea describes how people were affected with the disorder; writhe, twist, and turn in a constant, uncontrollable dance--like motion. Later, other descriptive names evolved. "Hereditary chorea" emphasizes how the disease is passed from parent to child. "Chronic progressive chorea" stresses how symptoms of the disease worsen over time. Today, physicians commonly use the simple term Huntington's disease (HD) to describe this highly complex disorder that causes untold suffering for thousands of families.