Huntington's disease (HD) is a genetic disease characterized by changes in movement and behavior. To date, little research has been done on individuals who are at risk for developing the disease. PHAROS is an observational study designed to monitor people who are at risk for developing HD, and to survey their attitudes and beliefs about their "at-risk" status. Investigators hope this study will help answer some important questions about HD, such as: 1.) What are the earliest signs of HD and when do they start? 2.) How accurate are the measures that physicians use in detecting the onset of HD? 3.) What factors influence the age at which a person carrying the HD gene develops the illness? and 4.) In a group of people at risk for HD, how many will develop signs of the illness over a minimum three-year period of observation?

Participants in the study will be evaluated every 9 months (for 5 years) using the Unified Huntington's Disease Rating Scale (UHDRS)--a clinical tool which looks at movement, psychological and behavioral function. The participants will also be asked to complete surveys about their mood, life events, and attitudes or beliefs about being at risk for HD. A blood sample, taken at the beginning of the study, will be confidentially tested to determine if the participant has the abnormal gene for HD. Neither the participant nor any of the PHAROS physicians or coordinators will learn the results of individual gene tests.

The scientists hope that this study will provide essential information for future trials of experimental drugs for HD.