Individuals, and where possible multiple family members, from families with inherited Parkinson's disease will be enrolled. We will also be enrolling people with sporadic Parkinson's disease. Known disease genes will be sequenced to look for mutations. In the event that no mutations are detected and there are samples from multiple family members, linkage analysis will be undertaken in an effort to identify a region or regions of the genome harboring defective genes that cause inherited Parkinson's disease. Candidate genes that reside in regions linked to the disease will be sequenced in effort to find mutations responsible for the disease.