Major national, state, and local systems reform efforts are under way to close the gap between science and service through implementation of a range of evidence-based practices (EBPs). A set of rhetorical distinctions and ensuing debates about the relevance of science versus service and efficacy versus effectiveness threatens to widen rather than close the gap. However, methodological and conceptual approaches, drawing upon strong theory-driven models, offer considerable promise for an integrated science on implementation effectiveness. This paper outlines some of the major scientific and policy challenges in strengthening the link between science and service in school psychology within the context of the papers in this series.