The second National Survey of Child and Adolescent Well-Being (NSCAW II) is a longitudinal study intended to answer a range of fundamental questions about the functioning, service needs, and service use of children who come in contact with the child welfare system. The study is sponsored by the Office of Planning, Research and Evaluation, Administration for Children and Families (ACF), U.S. Department of Health and Human Services (DHHS). It examines the well-being of children involved with child welfare agencies; captures information about the investigation of abuse or neglect that brought the child into the study; collects information about the child’s family; provides information about child welfare interventions and other services; and describes key characteristics of child development. Of particular interest to the study are children’s health, mental health, and developmental risks, especially for those children who experienced the most severe abuse and exposure to violence.