Background: Starting in 2013, VA's Opioid Safety Initiative expanded resources for pain management and successfully reduced high-risk opioid prescriptions. MISSION Act expansion of VA Community Care (CC) includes authorization for CC providers to prescribe opioids for outpatient treatment of acute and chronic pain, but charges VA with ensuring that these are safely and appropriately dispensed from VA pharmacies. Veterans who use both VA and non-VA services may be particularly at risk for opioid-related harms, but past work was conducted before MISSION Act implementation and mainly addressed services paid by non-VA insurers. Although the main goal of MISSION Act is to improve Veterans' health care access, it remains unclear how CC expansion has impacted opioid safety and patient-reported outcomes for Veterans. Significance & Impact: Reducing opioid-related harms and improving treatment for chronic pain are high- priority goals for VA HSRD and clinical services. Given increasing numbers of Veterans now using CC, there is an urgent need to better understand Veteran, community, and VA facility factors associated with receipt of CC opioids, and explore potential differences in higher-risk CC prescriptions, compared with VA-prescribed opioids. Moreover, examination of Veteran-centered pain outcomes will address the ORD-wide priority of increasing real- world impact of VA research. Innovation: This study will be the first to evaluate Veteran-centered outcomes associated with CC opioids, including functioning and health-related quality of life. The proposed design also includes multiple elements to rigorously address multilevel confounders, including variation in community opioid prescribing patterns. We use innovative causal estimation methods in our predictive models, in order to understand the relative importance of a variety of factors in contributing to likelihood of receiving CC opioids. Specific Aims: 1) Identify key multilevel predictors of receiving any CC vs. only VA-prescribed opioids for outpatient pain treatment, and evaluate potential differences in higher-risk opioid prescriptions; and 2) for a national prospective cohort of Veterans receiving any CC vs. only VA-prescribed opioids, examine differences in patient-reported outcomes and acute care episodes over 1 year. Methodology: First, we will conduct a retrospective analysis using national VA data from January-December 2021 to determine key Veteran, community, and VA facility factors that predict receiving any CC-prescribed opioids. Then, we will use propensity score adjusted models to examine differences in higher-risk opioids prescriptions between Veterans receiving any CC vs. only VA-prescribed opioids. For Aim 2, we will enroll a prospective national cohort to evaluate outcomes associated with receiving any CC vs. only VA-prescribed opioids. We will use survey data (at baseline and 1-year follow-up) to assess patient-reported outcomes (pain- related functioning, pain severity, quality...