This chapter of Foster Care and Best Interests of the Child provides a template for evaluating and reforming the U.S. foster care system to prioritize the best interests of children. We draw on the subspecialty of program evaluation to construct a logic model for the foster care system that connects the system’s inputs (resources), activities, outputs (intended results of fidelity to program model), and outcomes (intended intermediate and long-term impacts). We emphasize that most evaluations of foster care to date focus on process (activities and outputs) rather than long-term outcomes for children. We suggest a need for systemic and ongoing impact evaluation—a test of how foster care affects children’s later safety and well-being. In addition, the activities and outputs in our model largely reflect the processes and priorities suggested by federal policies and federal performance goals, rather than research evidence on the core components of an effective foster care system. We welcome a rigorous evaluation of our model’s core assumptions, specifically how system activities and outputs, such as referral to child or parent treatment services, permanency, or sibling placement, impact child safety and well-being.