Increasingly, funders across sectors are urging the use of evidence-based programs. Evaluators may be engaged in gathering program evidence, evaluating the scale-up of evidence-based programs, and/or addressing systems changes in which evidence-based programs are involved. Evidence-based practice as originally defined by the Institute of Medicine involves best research evidence, best clinical experience, and consistency with patient values. As the concept has been translated to other social sectors many issues arise about what constitutes “best research evidence” as well as the combination of these three factors. Often the underlying assumptions of certain research methods are not adequately considered in determining best research evidence. For example, certain research methods assume greater stability of the systems into which an evidence-based program is to be implemented than actually exists. In particular, certain research methods may be ignoring scientific knowledge about how complex systems function and their adaptive nature.#SystemsinEvaluation #2013Conference