Interest in high users of acute care continues to grow as health care organizations look to deliver cost-effective and high-quality care to patients. Since "super-utilizers" of acute care are responsible for disproportionately high health care spending, many programs and interventions have been implemented to reduce medical care use and costs in this population. This article presents a systematic review of the peer-reviewed and grey literature on evaluations of interventions to decrease prehospital and emergency care use among U.S. super-utilizers. Forty-six distinct evaluations were included in the review. The most commonly evaluated intervention was case management. Although a number of interventions reported reductions in prehospital and emergency care utilization and costs, methodological and study design weaknesses-especially regression to the mean-were widespread and call into question reported positive findings. More high-quality research is needed to accurately assess the impact of interventions to reduce prehospital and emergency care use in the super-utilizer population.