This article explores the use of integrated administrative data systems in support of policy reform through interagency collaboration and research. The legal, ethical, scientific and economic challenges of interagency data sharing are examined. A survey of eight integrated data systems, including states, local governments and university-based efforts, explores how the developers have addressed these challenges. Some exemplary uses of the systems are provided to illustrate the range, usefulness and import of these systems for policy and program reform. Recommendations are offered for the broader adoption of these systems and for their expanded use by various stakeholders.