The Design Phase of the National Study of Child Care Supply and Demand (NSCCSD) is now complete. The project was conducted under contract to the Office of Planning, Research and Evaluation (OPRE), Administration for Children and Families, U.S. Department of Health and Human Services by the National Opinion Research Center (NORC) at the University of Chicago with partners Chapin Hall Center for Children at the University of Chicago, Child Trends, and experts from various universities. Several products from the project are available, including a Final Report. The Design Phase final report provides an overview of the proposed study design and describes the specific policy research questions that would be answered through implementation of the proposed design. As directed by OPRE, we refer to the proposed main study that might implement the work of the Design Phase as the National Survey of Early Care and Education (NSECE). Subsequent chapters highlight additional design issues such as potential overlap with other federal surveys, cost drivers, and risks to the proposed design. As requested by OPRE, the project team evaluates six possible options for the study design. The report concludes with a set of descriptions for supplements to the main study that could enhance the value of the main study and fulfill additional policy research objectives.