The quality of public decision making depends significantly on the quality of analysis and advice provided through public organizations. Champions of “evidence-informed” policy making claim that rigorous evaluation practices can significantly improve attainment of cost-effective outcomes. After decades of experience, performance information is more sophisticated, but evaluation practices and capabilities vary enormously. Public agencies gather and process vast amounts of information, but there has been little analysis of how this information is actually utilized for policy and program improvement. This article examines how government agencies use evidence about policy and program effectiveness, with attention to four themes: (1) the prospects for improving “evidence-informed” policy making, (2) the diversity of practices concerning evidence utilization and evaluation across types of public agencies and policy arenas, (3) recent attempts to “institutionalize” evaluation as a core feature of policy development and budget approval, and (4) the relationships between public agencies and nongovernmental sources of expertise.