Research demonstrates that living in neighborhoods that are safe, healthy, and connected to highquality services, schools, and jobs can improve outcomes and economic mobility for children—if their families can afford to live in them. But how can we better understand which interventions most effectively support access to high-opportunity neighborhoods? And how can the Department of Housing and Urban Development (HUD) target resources to those interventions? As one approach, this paper proposes that HUD adopt a tiered-evidence framework, which has been used by several other federal agencies. This approach encourages grantees to explicitly incorporate evidence building into their work by requiring evaluation and providing greater levels of funding for interventions with stronger evidence. By applying evaluative rigor to innovative approaches, this demonstration would build evidence about a broad portfolio of strategies and expand knowledge about what works to improve economic mobility for families and children. This paper begins by discussing the state of research on opportunity and giving an overview of tiered-evidence grantmaking. It then proposes a HUD “opportunity demonstration,” discussing evidence standards, criteria for grantees, examples from existing research, and other key aspects of the demonstration. This paper is part of the Evidence-Based Policymaking Collaborative, which leverages the expertise of researchers from the Urban Institute, Brookings Institution, American Enterprise Institute, and the Pew-MacArthur Results First Initiative to create tools to inform evidence-based policymaking efforts. For more information, please see https://www.evidencecollaborative.org/.