Genes play a significant role in the risk of developing Parkinson's disease. Some genes have already been identified, but several others remain to be identified. One way to find these genes is to study very large families that come from unique human populations. We have identified and collected part of a very large family with PD in the Amish, who are both culturally and genetically separate from the general population. We have identified the likely locations for three genes using this family. The goal of our study is to expand this family and identify at least one of these genes.