The application of scientific data in the development and implementation of sound public policy is a well-established practice, but there appears to be less consensus on the nature of the strategies that can and should be used to incorporate research data into policy decisions. This paper describes the promise and the challenges of using research evidence to inform public policy. Most specifically, we demonstrate how the application of a large-scale data set, the National Core Indicators (NCI), can be systematically used to drive state-level policy decisions, and we describe a case example of one state's application of NCI data to make significant changes to its Intellectual and Developmental Disabilities waiver. The need for continued research in this area is highlighted.