Governments at all levels are tasked with administering public pro- grams that serve large numbers of people. The use of integrated data systems (IDS), which can be used to link administrative records from multiple public agencies into one database, offer a unique mechanism for providing the type of comprehensive information that is important for understanding the complex needs of vulnerable populations and for making data-based policy and program decisions that translate into more effective and efficient policies. In this paper, we draw on recent efforts to restructure Los Angeles County’s General Relief (GR) Program – a cash assistance program for indigent adults – as an example of how the effective use of IDS can play a crucial role in generating evidence that can guide important program and policy decisions.