Although the role for epidemiology is widely accepted in public health programs in general, its role in chronic disease programs is not as widely recognized. One possible barrier to improving epidemiologic capacity in chronic disease prevention and health promotion programs is that chronic disease program managers and public health decision makers may have a limited understanding of basic chronic disease epidemiology functions. We describe the assessment process of data collection, analysis, interpretation, and dissemination, and, using examples from two states, illustrate how this approach can be used to support program and policy development in three areas: by defining the problem, finding programs that work, and evaluating the effects of the program over time. Given the significant burden of chronic diseases in the United States, the scientific guidance provided by epidemiology is essential to help public health leaders identify priorities and intervene with evidence-based and effective prevention and control programs.