The National Survey of Child and Adolescent Well-being (NSCAW) is the only source of nationally representative, longitudinal, firsthand information about the functioning and well-being, service needs, and service utilization of children and families who come to the attention of the child welfare system. The first two cohorts of NSCAW were collected beginning in 1999 and 2008 and studied children who had been the subject of investigation by Child Protective Services. Children were sampled from child welfare agencies nationwide. In September 2015, the Office of Planning, Research and Evaluation, in collaboration with the Children's Bureau, awarded a contract to RTI International to carry out the third cohort of NSCAW (NSCAW III). An overarching goal of NSCAW III is to maintain the strengths of previous work, while: better positioning the study to address the changing child welfare population and increasing the project's overall utility.