American deaths from opioid overdose now approach 50,000 annually. While evidence shows that medications for addiction treatment (MAT) save lives, retaining patients in MAT programs is challenging. The U.S. Agency for Healthcare Research and Quality, on behalf of the U.S. Department of Health and Human Services, commissioned a rapid evidence review on the effectiveness of interventions to promote a broader understanding of the published literature on MAT retention among adults with opioid use disorder (OUD).