Congenital heart disease (CHD) is the most common birth defect, affecting about 0.8% of live births. Advances in recent decades have allowed >85% of children with CHD to survive to adulthood, creating a growing population of adults with CHD. Little information exists regarding survival, demographics, late outcomes, and comorbidities in this emerging group, and multiple barriers impede research in adult CHD. The National Heart, Lung, and Blood Institute and the Adult Congenital Heart Association convened a multidisciplinary working group to identify high-impact research questions in adult CHD. This report summarizes the meeting discussions in the broad areas of CHD-related heart failure, vascular disease, and multisystem complications. High-priority subtopics identified included heart failure in tetralogy of Fallot, mechanical circulatory support/transplantation, sudden cardiac death, vascular outcomes in coarctation of the aorta, late outcomes in single-ventricle disease, cognitive and psychiatric issues, and pregnancy.