The field of antithrombotic therapy is at present undergoing a rapid growth phase with the development of numerous agents that have the ability to inhibit various stages of the coagulation system and/or promote fibrinolysis. The development of these new antithrombotic drugs will provide pediatric patients and physicians with access to medications with unique properties that will challenge the current utilization of heparins and warfarin derivatives, many of which have been in existence for over 50 years. Establishing the benefits and risks in children of these new drugs relative to standard anticoagulation therapies will require trials that demonstrate convincing signals of non-inferiority or, ideally, superiority. The risks and harms of new agents will require adequate safety databases for bleeding and off-target toxicities that facilitate a clear understanding of net clinical benefit assessments. While new drug approvals in children will rely heavily on safety and efficacy findings from multicenter clinical trials, effectiveness in the real-world pediatric setting needs to be fully evaluated. Additionally, the role of new drugs in special pediatric subpopulations/settings and specific indications requires formal study. Physicians will also need comparative effectiveness data to inform clinical decision-making in regard to costs, benefits, and risks of “competing” drugs with differing mechanisms of action and/or modes of administration. As such pediatric drug development programs will usually build on adult evidence with the drug, it will be important that pediatric trials target relevant pediatric indications and generate as much complementary information needed to inform use of the drug in children while still being feasible. These challenges demand a cohesive approach to the design and execution of trials used for the development and approval of new antithrombotics and for post-approval comparative effectiveness and outcome studies, and were the impetus for the creation of a new, multinational, multidisciplinary, multi-institutional group of pediatric antithrombotic therapy trialists, the Pedi-ATLAS Group (Pedi-ATLAS), bringing together leading academic experts whose shared mission is to inform and optimize the design, execution, and oversight of pediatric antithrombotic therapy programs and individual trials, across all stages of drug development: from early stage development, through the new drug/device application process and regulatory agency approvals, to post-marketing studies.