||The National Children's Study (NCS) will examine the relationships between environmental exposures and the health and development of 100,000 children living in the United States. The children will be followed from before birth until age 21. This is a very large, complex, and ambitious undertaking. Scientifically robust exposure metrics that are both low cost and low burden are needed to link environmental exposures to health outcomes within this study. This workshop engaged scientists from the exposure, epidemiology, and health effects disciplines with the goal of identifying the most promising and practical exposure metrics to use in a study the size and scope of the NCS. Additionally, the group discussed knowledge gaps and potential exposure research that would fill these gaps and could be used to develop and evaluate the most efficient and effective metrics. The workshop results are intended to provide operational input to NCS in the near term and to stimulate research in the U.S. Environmental Protection Agency's (EPA's) Office of Research and Development (ORD), the National Institute of Environmental Health Sciences (NIEHS), and the exposure science community to advance the national children's research agenda. The workshop, held in Research Triangle Park, NC, on April 12 and 13, 2010, included the workgroup participants and invited scientists in the health and exposure fields from EPA, NIEHS, the NIEHS/EPA Children's Centers, the NCS Program Office, and the NCS Vanguard Centers. The workgroups presented overviews of their discussions along with their recommendations to the larger workshop audience. Workshop participants then discussed the workgroup proposals and recommendations with regard to scientific soundness, other schemes and options, feasibility, costs, participant burden, etc. Following all three workgroup presentations, opportunities for leveraging exposure research to evaluate proposed exposure metrics were discussed.