PROJECT SUMMARY/ABSTRACT The aims of the parent-study are to determine whether an adjunctive Mindfulness-Based Relapse Prevention (MBRP) treatment program improves medication adherence and reduces drug-use among opioid use disorder (OUD) patients receiving Medication Assisted Treatment (MAT). The broad long-term objectives of this project are to investigate how integrative pharmacological and behavioral treatments improve OUD treatment outcomes. The aim of this Administrative Supplement to Existing NIH-NIDA Grants proposal is to enhance the focus on racial health equity issues within the context of the randomized clinical trial (RCT) parent-study. Although a strong evidence-base exists supporting MAT for OUD, Black Americans often contend with additional inequities and hardships that may render such approaches less effective. Specifically, exposure to racial discrimination and subsequent race-based traumatic stress has been linked to drug misuse among Black Americans. However, these specific variables have not been examined in the context of OUD treatment. Moreover, there is limited research investigating the general role of race as a moderating factor on OUD treatment outcome. Mindfulness (i.e., present-centered nonjudgmental awareness), associates with self-care and addiction severity among with SUD and has been observed to function as a resilience factor that moderates the relationship between exposure to racial discrimination and psychiatric symptoms. MBRP is an evidenced-based behavioral intervention that has demonstrated efficacy in reducing drug-use among patients in SUD recovery. There is a notable dearth of research examining the role of race, exposure to racial discrimination, and race-based trauma symptoms on OUD treatment engagement or drug-use outcomes. As there is reason to believe that the mindfulness training included in MBRP may address race-based trauma symptoms in addition to MAT adherence and drug-use outcomes, further research is critical to promote mental health equity among Black Americans. The primary study aim is to determine whether MBRP, compared to treatment-as-usual (TAU), delivered to Black OUD patients receiving MAT through enrollment in a residential addiction treatment facility, results in (1) improved MAT adherence, and reduced drug-use following residential discharge and (2) reduced race-based trauma symptoms. As race-based trauma symptoms are understood to associate with SUD severity, A second study aim will test the extent to which exposure to racial discrimination and severity of race-based trauma symptoms predict pre-treatment (1) OUD severity and (2) poorer treatment adherence and increased drug-use measured following residential discharge for Black TAU participants (but not Black MBRP participants). As prior trauma exposure is observed to undermine treatment efforts for SUDs a third exploratory study aim will determine the extent to which reductions in race-based trauma symptoms (pre-to-post MBRP) mediate ...