GCBHS Intensive Engagement-MAT Project (Ie-MAT) - Greater Cincinnati Behavioral Health Services (GCB) will partner with Shelterhouse (SH), the largest homeless shelter in Cincinnati, and Cincinnati Health Network (CHN), a Health Care for the Homeless Program, to expand access to medication-assisted treatment (MAT) services for persons with opioid use disorder (OUD) in Hamilton County, OH. Ie-MAT will expand outreach, MAT, behavioral health treatment (BHT) and recovery support services (RSS) for complex, un- and underinsured clients who have a co-occurring mental health disorder (MHD) and/or are homeless. Rates of OUD and related harms are higher in vulnerable populations. Adults with MHD have a high prevalence of opioid use, four times that of people without MHD. OUD, coupled with MHD, is linked to overdose (OD), and increases HIV and hepatitis C infection. There is also a high prevalence of substance use disorders among persons experiencing homelessness (PEH), including higher rates of opioid misuse. Drug OD is the leading cause of death among PEH, with rates 30 times higher than the general population. Despite high rates of OUD and related harms, treatment initiation and retention are low. HC's treatment continuum lacks the capacity to provide OUD services to clinically vulnerable populations who are un- and underinsured. It only has 2 publicly funded Opioid Treatment Programs (OTP). Overall, the prevalence, multiplicity, and severity of behavioral health issues in the focus population, coupled with limited treatment options, demand a response to minimize the disparities present for persons with OUD who have a co-occurring MHD and/or are homeless. Ie-MAT will provide MAT, BHT, and RSS to 260 clients over the 5 year project (20 in year 1 an 60/year in years 2-5). Ie-MAT will expand access to MAT via targeted outreach to persons with OUD to facilitate treatment initiation and establish an OTP at SH that combines MAT, BHT and RSS. Outreach objectives focus on hiring and training Peer Recovery Coaches to conduct outreach and facilitate treatment entry. OTP objectives focus on collaborating with SH and CHN to establish a certified and accredited OTP in a homeless shelter. Key evidence-based practices include MAT, Motivational Interviewing, Cognitive Behavioral Therapy, Integrated Dual Disorder Treatment, and Contingency Management. Ie-MAT clients will include those enrolled in GCB's mental health programs and persons served through its PATH homeless outreach team. Mental health clients are 78% White and 52% female. Average age is 41. 22% are homeless. 9% are uninsured. 77% have a co-occurring substance use disorder. Mental health diagnoses include mood disorders, anxiety disorders, and schizophrenia/psychotic disorders. PATH clients are 73% male and 57% White. 25% are uninsured. 57% report a co-occurring disorder. GCB has the capacity, experience, and partnerships to expand MAT access to vulnerable populations in desperate need of treatment and RSS to reduce substance use and promote recovery.