OBJECTIVE:To address the clinical and regulatory challenges of optimal primary endpoints for bleeding patients by developing consensus-based recommendations for primary clinical outcomes for pivotal trials in patients within six categories of significant bleeding, 1) traumatic injury, 2) intracranial hemorrhage, 3) cardiac surgery, 4)gastrointestinal hemorrhage, 5) inherited bleeding disorders and 6) hypoproliferative thrombocytopenia. BACKGROUND:A standardized primary outcome in clinical trials evaluating hemostatic products and strategies for the treatment of clinically significant bleeding will facilitate the conduct, interpretation, and translation into clinical practice of hemostasis research and support alignment among funders, investigators, clinicians, and regulators. METHODS:An international panel of experts was convened by the National Heart Lung and Blood Institute and the United States Department of Defense on September 23rd and 24th 2019. For patients suffering hemorrhagic shock, the 26 trauma working-group members met for almost a year, utilizing biweekly phone conferences and then an in-person meeting, evaluating the strengths and weaknesses of previous high quality studies. The selection of the recommended primary outcome was guided by goals of patient-centeredness, expected or demonstrated sensitivity to beneficial treatment effects, biologic plausibility, clinical and logistical feasibility, and broad applicability. CONCLUSIONS:For patients suffering hemorrhagic shock, and especially from truncal hemorrhage, the recommended primary outcome was 3 to 6 hour all-cause mortality, chosen to coincide with the physiology of hemorrhagic death and to avoid bias from competing risks. Particular attention was recommended to injury and treatment time, as well as robust assessments of multiple safety related outcomes.