METHODS CORE SUMMARY The IMPACT (Optimizing EBP implementation for clinical IMPACT) Center is focused on optimizing evidence- based practice (EBP) implementation to improve treatment quality and clinical outcomes in youth mental health services. The Methods Core will develop, test, refine, and disseminate innovative, pragmatic methods for ad- dressing three challenges to optimizing EBP implementation: identifying and prioritizing implementation deter- minants, matching implementation strategies to prioritized determinants, and optimizing strategies before de- ployment and evaluation. Methods Core faculty will iteratively refine methods to address these challenges through exploratory projects and pilot studies conducted in collaboration with the Washington State EBP Initia- tive, an academic-community partnership that supports EBP delivery for children and adolescents. With each iteration, the methods will be evaluated with input from multiple stakeholders using Center-wide measures of acceptability, feasibility, and appropriateness. Refined methods will be transformed into pragmatic toolkits con- taining checklists, protocols, guidelines, templates, and resources that practice partners and researchers can use to support their implementation efforts or research projects. Aim 1 of the Methods Core focuses on refining a suite of state-of-the-art, practical methods for optimizing EBP implementation drawn from health care policy- making, public health and global development, product design and technology development, and Agile Science approaches to organize evidence and engage the end user in all aspects of implementation research. Specific methods include rapid evidence reviews and ethnography, design probes, causal pathway diagrams, user-cen- tered design methods, and optimization of research designs. These methods are new, recently introduced, or underutilized in implementation science and mental health services research. Methods Core Faculty will hold user-centered design sessions with stakeholders to ensure that refined methods are robust and pragmatic enough for use by the practice and research communities. Aim 2 will provide operational support to the research projects. The Methods Core is led by and staffed with methodological experts with sufficient FTE to work with the leads of exploratory projects and pilot studies to develop and refine their ideas and designs; participate in regular study meetings; contribute project- and study-relevant methods expertise; and provide general, statisti- cal, and qualitative analysis support. Aim 3 will support evaluation of the Center's research productivity and public health benefit. The Methods Core will develop metrics and methods to assess the quantity, quality, reach, and impact of the research products, as well as the reach and impact of the Center's research findings and methodological advances in the practice community. Aim 4 will disseminate the Center's methodological ad- vances and Center-generat...