PROJECT SUMMARY/ABSTRACT This is an administrative supplement in support of the parent grant (5R01AA027253), which allows modifications to be made to the study materials and procedures to address considerations for minoritized adolescent health disparities and the influences of social determinants of health on our study aims. The goal of the parent grant is to test the effectiveness of a promising computer-facilitated adolescent Screening and Brief Intervention (cSBI) system for delivery by pediatric primary care clinicians in a cluster-randomized controlled trial of patients ages 14-17 years with an upcoming annual well-visit who report unhealthy alcohol use or having ridden with an impaired driver in the past 12 months. Up to 40 pediatric primary clinicians across up to 10 practices are being recruited and randomized into either a Usual care or cSBI arm, and we expect at least 1,300 of their eligible patients will be enrolled. The parent study primary aims are to test the effect of cSBI on adolescents’ risk of heavy episodic drinking and on riding with an impaired driver/driving while impaired in the past 12 months. This trial is being conducted in the American Academy of Pediatrics’ Pediatric Research in Office Settings (PROS) national practice-based research network. This study is one of the largest pediatric trials to date of substance use screening and brief intervention in primary care settings. In this supplement, we seek to enhance understanding of disparities in substance use-related risk among adolescents who are sexual and gender minority (SGM). SGM adolescents are at greater risk of unhealthy substance use behaviors and substance use disorders compared to their non-SGM peers. Nonetheless, SGM adolescents have been underrepresented in primary care-based screening and brief intervention research studies aimed at early detection and prevention of substance use. Collaborating with researchers who have SGM expertise and with a community advisory board, we will develop recruitment materials that appeal to SGM adolescents in general pediatric clinic settings, as well as clinician guidance on SGM-friendly language and environment to enhance inclusion of SGM adolescents in the trial. We will add measures of sexual orientation and transgender status to more accurately identify SGM adolescents, and several measures accounting for social determinants of health that influence substance use risk (e.g., bullying, social support, school environment). The goal of adding these measures is to shed light on the role of SGM status and SGM-relevant social determinants of health exposure on substance use risk among adolescents in our study.