Background. Hepatitis C virus (HCV) is among the most common chronic viral infections in the U.S. and has surpassed all other infectious diseases as a cause of death. With the arrival of highly efficacious directly-acting anti-viral agents, treatment for HCV is now curative for the vast majority of patients. The VA is the largest provider of HCV care in the world and has scaled up efforts to identify and treat HCV. Unhealthy alcohol use is very risky for patients with HCV and influences HCV treatment adherence and outcomes. Despite the risks associated, many patients with HCV drink alcohol at unhealthy levels. While alcohol use was previously a contraindication to treatment, VA guidelines now recommend consideration of treatment for all patients with HCV, including those with unhealthy alcohol use, creating a prime opportunity for co-interventions focused on addressing unhealthy alcohol use during HCV treatment. HCV treatment-typically delivered over multiple visits- may provide time-limited opportunities for delivery of evidence-based alcohol-related interventions, but, due to previous contraindications, clinicians in HCV treatment settings are likely unprepared to offer evidence-based alcohol-related care. Practice facilitation is an effective multilevel implementation strategy that has promise for facilitating provision of alcohol-related care and ultimately improving alcohol use and HCV outcomes among patients with HCV and unhealthy alcohol use. Objective. The proposed study—conducted by a unique team of experts in implementation science and HCV and alcohol-related care—will use practice facilitation to increase provision of evidence-based alcohol-related care in HCV treatment settings and improve alcohol use and HCV treatment outcomes among Veterans with HCV and unhealthy alcohol use. Methods. The study will be guided by the Consolidated Framework for Implementation Research (CFIR) model. In Aim 1, we will use semi-structured qualitative interviewers with key clinical and patient stakeholders and rapid analytic methods to tailor the practice facilitation intervention. In Aims 2 and 3 we will disseminate the tailored intervention to 4 VA clinics in the western U.S. and then apply a Hybrid Type III implementation/ effectiveness design to evaluate the influence of the tailored practice facilitation intervention on implementation (primary) and clinical effectiveness (secondary) outcomes. Five implementation outcomes (acceptability, feasibility, adoption, penetration, and fidelity of alcohol-related care) and three clinical outcomes (alcohol use, HCV treatment completion, and sustained virologic response) will be evaluated using mixed methods. The primary implementation outcome (penetration) and clinical outcomes, will be evaluated using an interrupted time series design in which the implementation intervention is rolled-out in a stepped wedge fashion and clinics serve as their own controls (pre-post). Order in which the clinics receive the inter...