The current NIH-AARP substudy on Parkinson's disease will include approximately 9,000 participants from the NIH-AARP study - 3,000 of whom reported being diagnosed with Parkinson's disease on the most recent survey, and 6,000 control subjects. These study participants provide two saliva samples for genetic analysis and may be asked to complete a telephone interview. In addition, those with Parkinson's disease are asked permission to review medical information regarding their diagnosis.