Comprehensive information on disease incidence, treatment costs, and health outcomes is essential for informing and evaluating state health policies, but it is not readily available. To address these information needs, some states are developing all-payer claims databases. In a new Commonwealth Fund issue brief based on a study of current state and private initiatives, experts show how these databases are proving to be powerful tools for filling in longstanding gaps in health care information and providing essential trend data that will be needed to guide policymakers through the transitions health care reform will bring.