The purpose of this funding opportunity announcement (FOA) is to 1) support hypothesis driven clinical research to discover biomarkers that will improve the efficiency and outcome of Phase II clinical trials for Parkinson’s Disease (PD) and 2) support the collection of clinical data and new biological specimens that will be used for biomarker exploratory efforts under the NINDS Parkinson’s Disease Biomarkers Program (PDBP). Applications may include both of these goals if justified. Studies using either existing or new cohorts may be appropriate. For all applications, applicants must describe statistical justification for the number of subjects/samples proposed and a clear scientific rationale for the range and types of subjects/samples to be collected. Broad sharing of data and biological specimens with academic, industry and government researchers is a critical feature of the PDBP generally and of this FOA specifically, in order to provide valuable research resources for the scientific community to advance Parkinson’s Disease research in an efficient and effective manner (consistent with applicable laws, regulations, and policies); therefore, all subjects in any proposed study must be properly consented to allow appropriate sample and data distribution to researchers in academics and industry. The NINDS Repository and the PDBP data management resource (DMR) contracts will be utilized for the banking and distribution of new biospecimens and biological and clinical data, respectively. This FOA is only for studies related to human biomarkers; animal or other disease model studies are not responsive to this FOA. A timeline including milestones is required for all studies. Annual milestones will provide clear indicators of a project's continued success or emergent difficulties and will be used to evaluate the application not only in peer review but also in consideration of the awarded project for funding of non-competing award years.