PROJECT SUMMARY — RESEARCH PROJECT 3 (RP3) Implementation science holds great potential to increase the reach of effective interventions. However, there has been an underemphasis on prospective planning for and investigating of unintended consequences of imple- mentation efforts, particularly those that center equity. This can result in the creation and/or reification of existing inequities. Specifically, early mental health screening, identification, and intervention, while promising to improve outcomes for children and families due to the outsized impact on lifespan mental health, has the potential for negative unintended consequences, particularly for children and families from minoritized communities. Pro- spectively anticipating and evaluating unintended consequences in pediatric mental health prevention is increas- ingly recognized as ethically imperative because of the potential harm that could emerge from the implementation of evidence-based approaches. This study seeks to prospectively and concurrently explore and evaluate the unintended consequences that may occur with implementation of evidence-based practices for toddler mental health screening and intervention across all the Mental Health, Earlier (MHE) Center Projects. This work is in- formed by the Pullmann Compilation of the Ripple Effects of Implementing Children’s Mental Health Services, Rid’s Ethical Evaluation of Risks of Public Health Programs, and the Health Equity Implementation Framework. Foundational to our approach is the centering of the voices of our research and community partners to ensure holistic perspectives of unintended consequences resulting from the screening, identification, and intervention for toddler mental health risk. In Aim 1, we will conduct a “pre-mortem" with each MHE Project team, in which we will engage prospective hindsight to imagine the unintended consequences of each project’s imple- mentation and define equitable reach. In addition to producing Project-specific evaluation plans, these activities will also generate a generalizable methodological approach for future studies. In Aim 2, we will employ a multi- method approach to evaluate equitable reach and unintended consequences across context (caregivers, clinician, organizational [exploratory]) and across MHE projects. This cross-cutting study addresses a prominent limitation of many implementation studies to purposively evaluate and attend to unintended conse- quences that threaten equitable and ethical implementation of early identification and prevention of mental health problems in pediatric primary care. The MHE Center and its individual Projects, and its innovative trial design, provide a unique opportunity to study unintended consequences of implementation across the stages of the mental health risk identification-to-care cascade. This project is significant because it will inform the ideal process through which to engage in community-partnered, ethical, and equitable implementation of ...