PROJECT SUMMARY Adverse Childhood Experiences (ACEs) are defined as traumatic events occurring before age 18, such as maltreatment, life-threatening accident, harsh migration experiences or exposure to violence. ACEs are pervasive, with 45% experiencing at least one ACE and 10% experiencing three or more ACEs, placing them at high risk for negative life outcomes. ACEs are more prevalent among minority and immigrant communities due to exposure to poverty, discrimination, community violence, national disasters, and refugee experiences. ACEs screenings have potential value in identifying children experiencing toxic stress and the physical and mental health conditions associated with it such as asthma, ADHD and anxiety. Yet, they are seldom used in primary care during well-child visits. The Surgeon General of the state of California has addressed this care gap by issuing an ACEs screening policy. Starting January 2020, MediCal, California's Medicaid health care program, will reimburse primary care settings ($29) for using the Pediatric ACEs and Related Life-events Screener (PEARLS) tool to screen children for ACEs during wellness visits. Despite significant investment in California and nationwide, evidence of the public health value of universal child screening policies is unclear. Increased screening efforts often do not translate into higher access to care for children and may even exacerbate disparities by increasing stigma and reinforcing a deficit view of marginalized groups. These results have been attributed to a lack of rigorous studies testing implementation strategies suited for pediatric screening policies. This mixed-method study will fill this gap by refining and testing an implementation strategy using a multi-site control trial with a Federally Qualified Health Center in Southern California. Using the EPIS framework, we will employ a hybrid (type 2), randomized controlled trial using a stepped-wedge design (n=5 clinics) to test to test a central hypothesis that clinics employing a multifaceted implementation strategy will have higher fidelity and reach of the ACEs screening policy. A secondary hypothesis will examine the public health impact of the ACEs policy on child patient-level mental health service and symptom outcomes. Specific aims are: Aim 1. Refine a multifaceted implementation strategy to support the implementation of the ACEs screening policy in community-based clinics, and Aim 2. Pilot test the feasibility, acceptability, fidelity and reach of the implementation strategy and the impact of the ACEs policy on child patient-level outcomes. This project capitalizes on a rare opportunity to pilot test an implementation strategy to maximize the impact of a state-wide policy intended to improve child health in under-resourced settings.