Project Summary Opioid use disorders are a significant public health crisis, and medication treatment is the most effective intervention for individuals with opioid use disorder. State policies and initiatives have increased medication treatment utilization over the last decade, but increased utilization without attention to quality of care might limit the public health benefits of medication treatment. Many states have begun implementing policies and initiatives to improve quality, although with little empirical support of their effectiveness in real world settings. This project will characterize how quality care for Medicaid-enrollees receiving medication treatment for opioid use disorder and related health outcomes have changed over time, overall, and among historically underserved and high-risk populations. We will then examine the extent to which policies and initiatives that increase access and those aimed at improving quality are associated with better quality of care and related health outcomes, overall, and for historically underserved and high-risk populations