The National Survey of SSI Children and Families (NSCF) is the first nationally representative survey since 1978 of noninstitutionalized children and young adults who currently receive or formerly received Supplemental Security Income (SSI). Over 8,500 interviews were completed between July 2001 and June 2002. The primary objective of the NSCF is to provide data to support research and policy evaluation on the current cross section of children (ages 0 to 17) and young adults (ages 18 to 23) receiving SSI. Following that objective, the survey was designed to answer questions such as those presented below. What are the general characteristics of children and young adults receiving SSI and their families? What are the patterns of access to and utilization of health care among children and young adults receiving SSI? What services are utilized by children and young adults receiving SSI? What are the unmet health care and service needs of children and young adults receiving SSI? What costs are associated with caring for a disabled child? What is the impact on the family of having a disabled child? What is the status of young adults with disabilities as they make the transition to adulthood? How well are they prepared for that transition? In addition, the NSCF questionnaire and sample were designed to be comprehensive enough and large enough to address numerous additional policy issues as they emerge. The NSCF fills a gap in the data available to policy analysts by addressing a wide range of topics that cannot be addressed with SSI administrative data and by providing a large sample in contrast to major national survey databases that cover this target population fairly sparsely. A companion article to this overview describes general characteristics of SSI beneficiary children and their families (see Rupp and others 2005/2006, pages 21-48 of this issue). Other topics being examined include disability-related expenditures for SSI children and young adults and labor force participation of the parents of SSI children. The NSCF data files are accompanied by a detailed User's Manual, which includes a detailed codebook and information about the NSCF sample design, questionnaire design and content, data collection procedures, variable construction, editing, and variance estimation procedures. In order to facilitate research, the Social Security Administration published the NSCF Public-Use File and survey documentation on its Web site. These products are available at http://www.socialsecurity.gov/disabilityresearch/nscf.htm. The NSCF is an outstanding tool for conducting research and policy analysis regarding children and young adults receiving SSI.