The National HIV/AIDS Strategy and the promise of treatment as prevention have garnered considerable attention from the policy, practice, and scientific communities, with the treatment cascade becoming the sentinel image illustrating the domestic human immunodeficiency virus (HIV) epidemic. The cascade depicts prevalence estimates for sequential steps from HIV diagnosis through viral suppression, the most striking of which is that >50% of persons diagnosed with HIV are not in medical care. This heterogeneous group includes individuals not linked to medical care following HIV diagnosis and those entering care who are not retained, requiring reengagement from a range of community settings. This review synthesizes the state of engagement in HIV care in the United States, focusing on research, practice, and policy considerations. Included are conceptual frameworks, a review of health implications, measurement, monitoring, and evidence-based intervention approaches, and a look to the future in addressing the greatest challenge and opportunity facing our domestic HIV epidemic.