Abstract Young Black women bear a disproportionate burden of breast cancer (BC) mortality compared to Whites and are underrepresented in clinical studies. It remains critical to understand factors that contribute to the high mortality from BC among young Black women in order to improve outcomes. The higher BC mortality rate among young Blacks with BC is partly attributed to the disproportionately higher proportions who develop the aggressive triple-negative (TN) BC subtype. In addition to biologic factors, timely access to care, and lifestyle factors contribute to this disparity. Consequently, it has become imperative to look in detail within the Black population to evaluate the interplay between biologic and non-biologic contributors to existing disparities, and to better characterize the highly aggressive TNBC among young Black women based on distinct molecular subtypes. Ultimately, it is critical to assess both biologic and non-biologic factors in order to fully understand and address existing health disparities in young Black women. Through leveraging a prior population-based study of 460 young Black women with invasive BC in 2009-2012 (and recruitment of a representative sample of an additional 200 women diagnosed in 2013-2014), we plan to: 1) assess the contribution of biologic and non-biologic factors on high mortality rates observed among young Black women with BC and generate a risk score, to help identify those at risk for poorer outcomes, and 2) investigate molecular features of the subgroup with TNBC. We hypothesize that biologic (including tumor gene expression profiling) and non-biologic factors contribute to existing disparities in BC survival among young Black women. Furthermore, we hypothesize that Blacks have a higher proportion of aggressive subtype of TNBC. To our knowledge, this is among the largest population-based cohorts of young Black women with breast cancer. Ultimately, our study presents a unique opportunity to quantify biological and non-biological factors associated with BC-specific survival, and further characterize TNBC among Black women. Given that prior interventions have too narrowly focused on the patient as the agent of change without meaningfully impacting the BC mortality disparity, it is important to consider patient, provider and system level approaches concurrently to drive system change and close the mortality gap.