ABSTRACT The overarching goal of this R21 grant proposal is to evaluate racial and ethnic disparities in patient outcomes, racial and ethnic differences in the three key intra-arrest interventions (time to shock delivery; time to epinephrine administration; time to termination of resuscitation), and quantify the impact of the racial and ethnic differences in time to return of spontaneous circulation (ROSC) on outcomes disparities among adult patients with in-hospital cardiac arrest (IHCA) using the American Heart Association Get With The Guidelines– Resuscitation (GWTG–R), a multicenter prospective quality improvement registry of IHCA in the United States. IHCA is a critical public health issue, affecting approximately 292,000 Americans annually. Despite various efforts, the mortality after IHCA remains high, and only 18.8% of patients survive to hospital discharge, highlighting its significance in the nation. Prior studies reported racial disparities in patient outcomes following IHCA, with Black patients experiencing unfavorable outcomes than White patients. However, little is known about outcomes among Hispanic patients compared with Black and White patients. Moreover, the underlying mechanisms of racial disparities between Black and White patients remain unclear. Racial and ethnic differences in intra-arrest resuscitative interventions are the potential source of the health inequity. Evaluating racial and ethnic disparities in intra-arrest resuscitative interventions will enhance our understanding of these potential disparities in the process of care and identify modifiable areas for improvement in IHCA care. We will investigate three crucial intra-arrest resuscitative interventions: time to shock delivery, time to epinephrine administration, and time to termination of resuscitation (TOR)—all are directly linked with patient outcomes. To fill the crucial gaps in knowledge and mitigate the health inequity in IHCA, we will investigate patients’ racial and ethnic disparities in time to ROSC, survival to hospital discharge and favorable functional outcome at hospital discharge across Hispanic, Black, and White patients (Aim 1); evaluate patients’ racial and ethnic differences in time to shock delivery (Aim 2A), epinephrine administration (Aim 2B), and TOR (Aim 2C); and quantify the impact of racial and ethnic differences in time to ROSC on racial and ethnic disparities in survival and favorable functional outcome after IHCA using causal mediation analyses (Aim 3). In our project, we will employ IHCA as a representative case for emergent conditions, with the objective of evaluating racial and ethnic disparities in outcomes and intra-arrest practices. We anticipate that our study will identify specific areas where interventions can be implemented to mitigate the health inequity in IHCA.