The goal of the project is to inform policymakers considering use of Section 1115 demonstration waivers to expand access to substance use disorder (SUD) treatment. The study will focus on Virginia and Maryland, two states using such waivers to increase Medicaid recipients’ access to the full continuum of addiction treatment services; improve quality of care and coordination for recipients with co-morbid physical and mental health problems; and reduce overdose deaths, while remaining budget neutral and not shifting the balance of care toward more institutionally-based forms of treatment. The research team, a collaboration between Virginia Commonwealth University and the Hilltop Institute at the University of Maryland, Baltimore County, will analyze Section 1115 SUD waivers in Virginia and Maryland to understand differences in how the two states implemented them and to assess: (1) changes in SUD diagnoses, access, utilization and outcomes post-implementation; (2) differences in the extent of change between the two states, especially differences associated with Maryland’s earlier ACA Medicaid expansion; and (3) the contribution of changes in residential capacity to changes in SUD treatment. Deliverables will include a project work plan and final narrative and financial reports. The grantee will also produce paper(s) suitable for publication and present findings at national research meetings and to other stakeholder audiences as appropriate, including policymakers at the federal, state, and local levels, as part of the deliverables for this grant.