The child welfare system has a responsibility to provide healthy environments for children who are removed from the care of their biological families. An important indicator of success in this endeavor is variations in child functioning following admission into foster care. Maltreated children are already at risk for difficulty adjusting to new environments and creating new relationships. This dissertation sought to explore the effect of change during foster care on child functioning. The effects of various types of change on children who were provided with treatment foster care services were evaluated using the Child and Adolescent Functional Assessment Scale (CAFAS®) as a measure of child functioning. Results indicated that placement change and foster sibling presence negatively impacted child functioning, but that caseworker contact, foster sibling removal, and caseworker change positively impacted child functioning. Policy and practice implications emphasize the positive impact of single-child foster care placements, reduced volatility within foster child environments and relationships, and increased caseworker contacts. Future research should examine factors that mediate the relationship between systemic volatility within the foster care system and child functioning. / text