Abstract Despite long-standing gender parity in the number of medical students, women remain underrepresented in the senior ranks of the physician-scientist workforce, and research suggests that the mid-career transition is a point at which many careers stall. Research is needed to identify effective, scalable interventions to promote the careers of female physician-scientists throughout the career cycle, and particularly at the mid-career stage when they are positioned to ascend to senior leadership. We previously generated actionable insights by investigating the early career experiences of a national cohort of highly apt, research-oriented faculty members with clinical doctorates: recipients of NIH K08 and K23 career development awards. This cohort has been uniquely informative given its relative homogeneity in terms of high aptitude and motivation to pursue careers as clinician-researchers and the resources initially invested in supporting their advancement to independence. Ten years after our original study, we now propose to evaluate the impact of an intervention for women in this national K-awardee cohort as its members enter mid-career, a time when individuals begin to gain resources and influence in the form of endowed professorships, honorary society participation, and leadership positions. Although there is strong evidence to suggest a need for an intervention to promote women’s careers in biomedical research and some evidence to inform intervention design, we propose a brief period of observational research to optimize the intervention for this particular mid-career cohort, who reached this critical transition point just as the #metoo movement and potential backlash (including possible withholding of sponsorship by senior men) developed. Therefore, in our first two aims, we propose survey and qualitative methods to illuminate the mechanisms driving differences in career outcomes by gender in the post-#metoo era and to explore the impact of the intersection of gender with other categories of disadvantage such as race or sexual orientation, in order to inform the final design of our intervention. In our third aim, which is the primary focus of the grant, we will implement and evaluate a peer mentorship intervention designed to mitigate the differential challenges faced by women as they navigate the transition to senior leadership. We will compare outcomes, including career advancement, productivity, and burnout among women randomized to either a control arm provided with curricular materials or an intervention arm provided with the same materials but also engaged in peer mentorship teams modeled on the Leadership Learning Model Framework developed for the Executive Leadership in Academic Medicine Program, which is partnering with us in this work. This study will be the first to test a readily scalable peer mentorship intervention that targets individuals at the critical mid- career transition to senior leadership in biomedical research ...