PROJECT SUMMARY/ABSTRACT Excessive drinking results in tremendous economic and social costs and is a leading cause of preventable death in the US. Only a small minority of people with alcohol use disorder (AUD) receive appropriate services, and there are large disparities in access to alcohol health services for people based on race/ethnicity, gender, socioeconomic status, and urbanicity. The proposed study will answer pressing questions about how to reduce disparities in access, using simulation modeling to examine whether universal increases in access to evidence-based practices (EBPs) such as screening, brief intervention, and referral to treatment (SBIRT) or medication-assisted treatment can reduce disparities, or whether more targeted efforts to improve access are needed to reach high-priority population subgroups. Simulation models are well-suited for identifying unintended consequences of interventions implemented in complex systems, as well as outcomes that may occur years after implementation. By projecting intervention effects across population subgroups over time, simulation modeling can help identify and prioritize types of alcohol health services interventions to reduce AUD disparities. Although simulation methods are being used to address the opioid crisis, to date there is no published simulation model comprehensively describing the continuum of alcohol health services in relation to AUD disparities. The proposed study fills this gap by simulating effects of increased access to alcohol health services across the continuum of care from SBIRT, to specialty care (including AUD medications) and informal treatment (including 12-step groups like Alcoholics Anonymous), in relation to health disparities. First, we will build and calibrate a microsimulation model of alcohol health services for people with mild, moderate, and severe AUD, guided by a conceptual model that includes barriers to treatment at the individual, organizational, community, and policy levels. Next, we will use a geographically situated simulated population representing the large, demographically and geographically diverse states of California and Texas to make long-term projections for AUD severity and recovery for key population subgroups over time. Finally, informed by theories of healthcare access and utilization, we will project changes in AUD treatment disparities under several enhanced conditions to identify the mix and distribution of services that would best reduce disparities, and we estimate costs and benefits of improved service access. Study Aims are to assess effects of (1) universal implementation of EBPs in traditional and non-traditional settings and (2) improving accessibility, availability, affordability, and acceptability of alcohol health services on disparities, and to (3) estimate cost and cost-effectiveness of these changes. Results will provide detailed information to inform service planning by states, counties, and communities to improve health...