ABSTRACT Venous thromboembolism (VTE), consisting of deep vein thrombosis (DVT) and pulmonary embolism (PE), affects approximately 1 in 200 hospitalized patients <21 years old, and annual health care costs of pediatric VTE can be estimated at $72M in the U.S. alone. As in adults, PE can be fatal in pediatric patients, and DVT can result in long-term chronic venous insufficiency (the post-thrombotic syndrome [PTS]). However, treatment and prevention of VTE with anticoagulant medications carries a risk for bleeding, which can be life-threating. In order to optimize net clinical benefit, pediatric subpopulation-specific risks assessment models (RAMs) must be developed and validated, and prognostic factors identified, in patients <21 years old. This has been the focus of my career-long research work and mentorship. Recently, my multinational collaborators and I have made significant advances in pediatric VTE treatment via publication in JAMA of practice-changing findings from the U01-funded Kids-DOTT randomized trial on duration of anticoagulation for acute VTE in patients < 21 years old, and have also generated published evidence on several subpopulation-specific RAMs over the past 3 years. Yet, critical knowledge gaps remain regarding RAM development in critically ill patients and the investigation of prognostic markers for clinically-important VTE outcomes, including recurrent VTE and PTS. In this K24 proposal, I will mentor six junior faculty clinical/translational researchers focused in VTE prevention and treatment, from across four pediatric disciplines (hematology, critical care medicine, hospital medicine, pharmacy) and three academic institutions (Johns Hopkins University [JHU], University of Alabama at Birmingham, Harvard University), including three females and three individuals of color or historically underrepresented backgrounds. The proposed studies build upon existing collaborations in data science and biomarker-informed prognostic modeling, and will leverage data and/or biospecimens from multicenter studies in which I play a leadership or senior collaborating role. In each project, the junior faculty mentee will also have direct interaction with new or existing patients on study, for de novo data collection. Under this K24 proposal, I will enhance my mentorship expertise via the JHU Master Mentor Program and grow my knowledge in both Bayesian methods and plasma proteomics through online coursework and regular interactions with experts in these fields, who also serve as co-investigators in the proposed projects. By facilitating the expansion of my interdisciplinary research in pediatric VTE and strengthening my abilities to successfully mentor future junior faculty clinical and translational researchers in the field of pediatric VTE from across a range of disciplines and institutions, the proposed K24 will have significant impact as a force-multiplier in the pediatric VTE field.