Project Summary An estimated 40.3 million adults and adolescents needed treatment for substance use disorders in 2020. Yet only 6.5% of those needing treatment received it. Access to high-quality care remains a significant challenge. In the past decade, private equity (PE) firms have acquired numerous substance use disorder (SUD) treatment facilities, although evidence on the extent of these acquisitions is scarce. SUD treatment centers are attractive targets for private equity acquisition due to increased need for SUD treatment, increased health insurance coverage, and expansions in coverage of SUD treatments, all of which increase demand for treatment. Opportunities for efficiencies due to the fragmented nature of the market and changes to regulations regarding buprenorphine prescribing have the potential to increase profits. Commentators have raised concerns that a focus on short term profits may lead to quality declines in private equity-acquired facilities. Similar acquisitions in other areas of health care have resulted in declines in quality and increases in mortality. In this supplement, we will, for the first time, comprehensively catalog and describe Opioid Treatment Program (OTP) acquisitions by private equity investors from 2013-2022. This supplement would fund a predoctoral candidate for 10 months to examine the effects of private equity specifically in opioid treatment programs. The proposed project will first describe the number, trends and geographic distribution of PE acquisitions of Opioid Treatment Programs a subset of SUD treatment facilities. We will also include information on PE-backed newly established OTPs (Aim 1). We will then assess whether these acquisitions are associated with changes in measures of Medicaid- financed methadone treatment quantity and quality at acquired OTPs, relative to non-acquired OTPs (Aim 2). The proposed Mentorship Plan includes a mentorship team consisting of researchers with expertise in health policy and economics, addiction medicine and Medicaid policy. Goals of the Career Development Plan include enhancing research knowledge of state Medicaid reimbursement policy, Medicaid claims analysis, and addiction medicine. Goals will be achieved through the proposed supplement research and professional development activities: successful execution of project milestones, didactic training, internal work-in-progress presentations, formal external presentations, and mentorship and interactions with co-investigators of the parent award. The proposed supplement plan will facilitate the candidate’s transition to a faculty position as an addiction policy researcher.