Greater numbers of young children with complicated, serious physical health, mental health, or developmental problems are entering foster care during the early years when brain growth is most active. Every effort should be made to make foster care a positive experience and a healing process for the child. Threats to a child's development from abuse and neglect should be understood by all participants in the child welfare system. Pediatricians have an important role in assessing the child's needs, providing comprehensive services, and advocating on the child's behalf. The developmental issues important for young children in foster care are reviewed, including: 1) the implications and consequences of abuse, neglect, and placement in foster care on early brain development; 2) the importance and challenges of establishing a child's attachment to caregivers; 3) the importance of considering a child's changing sense of time in all aspects of the foster care experience; and 4) the child's response to stress. Additional topics addressed relate to parental roles and kinship care, parent-child contact, permanency decision-making, and the components of comprehensive assessment and treatment of a child's development and mental health needs.