ABSTRACT Improving inclusion and engagement of diverse populations in clinical research can broaden the relevance and translation of research findings into practice. Many communities are under-represented in health research due to: lack of knowledge about clinical research, mistrust, lack of access, geo-location, and social factors. Lack of knowledge about how research works and how it can benefit communities is a common reason for non- engagement, especially if research is carried out in academic medical institutions and locations where a significant proportion of people do not access care. Providers and community health groups often lack knowledge and training about clinical research and how it may or may not align with patients’ and community priorities. To our knowledge, there is no compendium of tools aimed at advancing inclusion and engagement of diverse and minority populations in clinical research. In this supplemental application, we propose to develop such a toolkit. The goal of the toolkit will be to provide researchers and community partners a guide to taking the individual, cultural, and structural perspectives into consideration when proposing clinical research. We are specifically interested in advancing engagement in research and trials that deal with substance use, and especially opioid use disorder (OUD), in association with our HEAL funding from the National Institute on Drug Abuse for the Southwest Clinical Trial Node of the NIDA Clinical Trials Network. We propose to conduct this work in southern New Mexico, an area with a highly diverse population, where many groups are impacted by OUD and there has been low clinical trial engagement. Using existing materials and resources, we will examine, adapt, and test these to produce a clinical research engagement toolkit that can be used to enhance engagement in clinical research by addressing both individual and structural barriers to engagement. The Health Beliefs Toolkit includes items that can be adapted to assess individuals’ knowledge of health, their perceived susceptibility to illness, and barriers (including personal values and beliefs) or benefits to health research engagement. We will review and adapt health literacy tools to develop ‘clinical research literacy’ tools for toolkit inclusion. We will also develop components that aim to enhance communication about clinical research with motivational interviewing techniques. Finally, we will develop an assessment of structural vulnerability adapted from the structural vulnerability checklist for health care providers. The target groups we will work with to adapt, develop and test the toolkit will include: primary care providers, promotora/es (community health workers), peer counselors, agency representatives, and patient and non-patient groups. We will use a mixed-methods approach to adaptation and evaluation of the proposed toolkit. Ripple Effects Mapping will be conducted as part of the final evaluation. The proposed EXPLORE ...