The physician-scientist workforce persistently fails to reflect the racial and ethnic composition of both the United States' (U.S.) general population and medical schools. There is growing attention in medical education to the importance of professional identity formation, defined as the development of values, beliefs, aspirations, and sense of affiliation aligned with the norms of the profession. There is evidence that experiences during medical school play a critical role in shaping physician-scientist professional identity formation, and that these experiences differ between underrepresented in medicine (URiM) and non-URiM students. Yet little is known about training practices and organizational characteristics of medical schools with the greatest success in equitable physician-scientist professional identity formation among URiM medical students, including Blacks, Hispanic/Latinx Americans, and Native Americans. We propose a multi-stage mixed methods study to identify the training practices and organizational characteristics of MD programs with greatest success in equitable physician-scientist professional identity formation among URiM single-degree medical students, relative to non-URIM students. This objective will be achieved through the following specific aims: 1) use data from the Association of American Medical Colleges [AAMC] Graduation Questionnaire [GQ] to identify MD programs which consistently demonstrate greatest and least success in equitable physician-scientist professional identity formation among URiM medical students relative to non-URiM students; 2) develop hypotheses about best practices and organizational characteristics for promoting equitable physician-scientist professional identity formation by conducting in-depth qualitative interviews at MD programs demonstrating the greatest and least success in equitable physician-scientist professional identity formation, and; 3) evaluate associations between practices and organizational characteristics identified in Aim 2 and consistent equity in physician-scientist professional identity formation through a national survey to identify best practices and characteristics that are broadly applicable to U.S. MD programs. This study is significant because it will provide information that can inform efforts to enhance the racial and ethnic diversity of the physician-scientist workforce. Our primary outcome of institution-level equity in physician-scientist development between URiM and non-URiM students is innovative and practical. Whereas rates of physician- scientist development may differ between MD programs, due to characteristics such as research intensity of the school, disparities in rates of physician-scientist development between non-URiM and URiM students within MD programs signal potential issues regarding egalitarian distribution of resources and discriminatory practices. Dissemination will take the form of scholarly publications and real-world communications (toolkit, websi...