Abstract-The National Heart, Lung, and Blood Institute convened a working group on outcomes research in cardiovascular disease (CVD). The working group sought to provide guidance on research priorities in outcomes research related to CVD. For the purposes of this document, "outcomes research" is defined as investigative endeavors that generate knowledge to improve clinical decision making and healthcare delivery to optimize patient outcomes. The working group identified the following priority areas: (1) national surveillance projects for high-prevalence CV conditions; (2) patient-centered care; (3) translation of the best science into clinical practice; and (4) studies that place the cost of interventions in the context of their real-world effectiveness. Within each of these topics, the working group described examples of initiatives that could serve the Institute and the public. In addition, the group identified the following areas that are important to the field: (1) promotion of the use of existing data; (2) O utcomes research is a field directed to the study and eventual improvement of the end results of health care. 1 "Outcomes research" can be defined as the study of the delivery and consequences of health care on outcomes from the perspective of patients, practitioners, and the healthcare system. Outcomes research focuses particularly on providing evidence to assess and promote the effectiveness of therapeutic interventions, enhancing the migration of best practice to clinical practice, improving decision making, elevating the quality of care, and supporting the optimal allocation of resources for all patients. Consequently, the research has a proximate and immediate connection to patient care and healthcare delivery.Despite the accelerating pace of basic and traditional clinical research in cardiovascular disease (CVD), there remains ample opportunity to improve clinical practice and healthcare delivery. Clinicians and policy makers often lack knowledge about gaps in healthcare delivery, disparities and inefficiencies, ineffectiveness of seemingly "proven" strategies, and the cumulative impact of interventions on the lives of patients. There is also a dearth of knowledge about how best to promote CV health and healthcare delivery in practice. 1-3 These gaps in knowledge hinder our ability to advance medical care even as our understanding of health and disease expands. We lack basic information about contemporary patterns of care and have a limited array of valid tools and strategies to quantify and improve clinical performance. We often demonstrate efficacy of treatments but commonly do not know the effectiveness of different clinical strategies in actual practice, as well as the impediments to achieving the true potential of the best interventions. We often do not know the impact of clinical and policy strategies on a broad range of patient outcomes, other than mortality and events. We lack basic information that would enhance clinical decision making from the patient's perspective. We lack evidence a...