PROJECT SUMMARY In recent years there has been a marked surge in opioid overdose deaths across Black and Latino populations. Addiction treatment, which includes medications for opioid use disorder (MOUD) such as buprenorphine, decreases fatal opioid overdoses. Yet Black and Latino individuals face substantial disparities in access to MOUD and addiction treatment. The emergency department (ED) represents an emerging setting to initiate MOUD and provide linkage to ongoing addiction treatment to Black and Latino individuals with untreated opioid use disorder (OUD). However, little is known about the barriers and facilitators that Black and Latino individuals encounter to engage in addiction treatment subsequent to an ED visit. Moreover, less is known about the differences in ED presentation for opioid overdose, polysubstance use, major depressive disorder, and stigma within these populations. Filling these knowledge gaps are important because opioid overdose, polysubstance use, major depressive disorder, and stigma have each been linked to worse treatment outcomes. Further, eliciting barriers and facilitators can inform future ED-based interventions to enhance engagement in addiction treatment among Black and Latino individuals with untreated OUD. The goal of this proposal is to evaluate disparities in access to addiction treatment and elicit potential targets for ED-based interventions that enhance engagement in addiction treatment among Black and Latino populations. The specific aims are to: 1) conduct a qualitative study focusing on patterns of barriers and facilitators to engaging in addiction treatment among Black, Latino, and non-Latino White patients receiving ED-initiated buprenorphine treatment with a referral for continuation of OUD treatment outside of the ED and 2) evaluate differences among Black, Latino, and non- Latino White ED patients with untreated OUD on factors previously identified as predictors of worse treatment outcome, including opioid overdose, polysubstance use, major depressive disorder, and stigma, using supplemental analyses of data collected in CTN 0099. To accomplish this, we will conduct both semi-structured individual interviews of Black, Latino, and non-Latino White participants enrolled in CTN 0099 after they have completed their final 30-day assessments and supplemental analyses from data collected in CTN 0099. Study findings will inform the development of an ED-based intervention that enhances engagement in addiction treatment among Black and Latino populations subsequent to ED visit.