ABSTRACT Despite high rates of need, REM youth are significantly more likely to prematurely dropout of mental health services as compared to their White peers. This is due in part to poor therapeutic alliance and concerns about treatment relevance and acceptability. Existing engagement interventions are limited, with few addressing treatment retention for REM youth at risk for depression and suicide. Measurement-based care (MBC) is the use of patient-reported progress data throughout mental health treatment to promote collaborative, patient- centered treatment plan adjustments. MBC is an outstanding candidate to improve treatment engagement due to its focus on personalized treatment and is also highly effective when integrated in depression treatment. Yet, MBC could be tailored to better address the unique needs of REM youth. MBC has not been examined as a treatment engagement strategy for REM youth with depressive symptoms or suicide risk. Further, no clinical protocols, guidelines or training supports exist to facilitate clinician use of MBC with REM youth and their caregivers. Based on past research, we have developed a theoretically-driven, culturally-tailored MBC approach, Strategic Treatment Assessment for Youth (STAY). STAY targets therapeutic alliance and treatment relevance and acceptability (concerns particularly relevant to REM youth and their caregivers) to improve treatment retention, depression symptoms and suicide outcomes. Pilot data suggest STAY is acceptable, feasible, and appropriate. In Aim 1, we will refine the preliminary STAY protocol and implementation plan to support delivery in a wide variety of clinical contexts. A user centered design approach including cognitive walkthroughs and lab-based testing with N=12 expert stakeholders will be used to rapidly refine prototype versions for usability. In Aim 1, we will also develop STAY instrumentation for clinician fidelity, knowledge, skills, and attitudes to be piloted in Aim 2. Aim 2 will involve a pilot effectiveness-implementation Hybrid Type 2 trial to examine the feasibility, acceptability, appropriateness, and initial effectiveness of STAY as compared to an active control condition (MBC As Usual). Clinicians (N=20) at three community mental health clinics will be randomly assigned to STAY or MBC As Usual and N=60 adolescent patient/caregiver dyads (Total N=120) who meet inclusion criteria will also be recruited to participate. Initial effectiveness of STAY on treatment engagement mechanisms (treatment alliance, relevance), service outcomes (treatment attendance, engagement, completion) and youth outcomes (depression, suicidality) will be assessed. This pilot will inform optimal study procedures, measures, and sites for a fully-powered Hybrid Type 2 trial. Disparities in depression and suicide rates are a national public health crisis. This project offers an innovative, culturally-tailored approach to retain REM youth in mental health services, reduce disparities and impr...