PROJECT SUMMARY As the nation continues to grapple with a rapidly changing epidemic of opioid overdose and mortality, there has been increasing public attention devoted to expanding access to opioid use disorder (OUD) treatment. While Medicaid is positioned to be a key policy lever to improve access to OUD treatment and reduce mortality among vulnerable populations, many state Medicaid programs do not cover the full continuum of OUD treatment and use utilization management parameters that may restrict access. Moreover, most state Medicaid programs contract with managed care organizations (MCOs). While over 70% of all Medicaid enrollees participate in MCO plans, little is known about how these plans cover OUD treatment. To fill this gap in the scientific evidence, we will conduct the first multi-state study of the effects of Medicaid MCO coverage and utilization management design on OUD treatment receipt and outcomes. The study will break new ground by encompassing all MCO plans, across multiple states, for the full continuum of treatment. We also propose to make use of innovative random auto-assignment methods in two state Medicaid programs. Our specific aims will include: estimating how state Medicaid program contractual regulations and oversight are associated with MCO plan level coverage and utilization design; estimating how MCO plans’ coverage and utilization management design are associated with progression through the Cascade of Care (diagnosis, engagement, medication initiation, and retention); and estimating how MCO plans’ coverage and utilization management parameters are associated with opioid-related emergency department visits, hospitalizations, and mortality. The proposed study will be the first comprehensive investigation of the effects of MCO coverage for OUD treatment services and medications on treatment receipt and outcomes – evidence without which the care of a large fraction of the OUD population is compromised. The study will also produce new insight into how states are regulating and monitoring MCO plan coverage and utilization management design. In the midst of the deadliest drug epidemic in the nation’s history, evidence regarding the impact of Medicaid MCO coverage for OUD treatment is urgently needed. This research will equip policymakers with evidence-based guidance on how to structure MCO contractual arrangements to ensure appropriate and efficient access to OUD treatment.