Project Abstract Improving HIV and Opioid Use Disorder (OUD) management and implementation for criminal justice (CJ)- involved individuals requires effective approaches to screening, linkage and adherence to integrated services across community agencies and service providers. Community reentry represents a critical opportunity to link individuals to HIV prevention and treatment and OUD service providers. In response to RFA DA-20-028, our proposed study called Addressing risk through Community Treatment for Infectious disease and Opioid use disorder Now (ACTION) among justice-involved populations, is a 5-year Hybrid Type 1 Effectiveness- Implementation RCT that compares two models [Patient Navigation (PN) or Mobile Health Unit (MHU) service delivery] of linking individuals recently released from prison and jail to the continuum of community-based HIV and OUD prevention and treatment service cascades of care. A total of 864 CJ-involved individuals who are being released to 2 CT communities (New London and Windham/Tolland Counties) & 2 TX communities (Dallas and Tarrant Counties) with pre-arrest histories of opioid/injection drug use and are living with or at-risk of HIV will be randomized to receive at post-release either: a) a PN system for care, wherein patient navigators will link study participants to community-based service providers during the 6-month post-release intervention period; those without HIV will be provided access to PrEP services, and those living with HIV will receive access to ART services, or b) services delivered via a MHU, wherein study participants will be linked to a MHU within their community where they will receive integrated PrEP/ART, MOUD, harm reduction services on the MHU during the 6 month post-release intervention period. There are 2 specific aims: Aim 1 (Intervention Effectiveness): To compare the effectiveness of the use of PN vs. MHU service delivery on participant length of time to taking initial post-release PrEP (prevention)/ART (treatment) medication within 6 months following release from custody. Secondary outcomes will examine the continuum of PrEP and HIV care outcomes, including (but not limited to) the following additional measures: HIV viral suppression for PLH, PrEP adherence, HIV risk behaviors; HCV measures such as HCV testing & linkage to treatment; sexually transmitted infection (STI) incidence (GC/ Chlamydia/ Syphilis and HBV); and primary medical care appointments. Importantly, we will also assess OUD and SUD-related measures: OUD/ SUD diagnoses, MOUD prescription receipt &retention, opioid & stimulant use, & overdose incidents. Aim 2 (Implementation): To evaluate PN and MHU feasibility, acceptability, and costs. Primary implementation outcomes include feasibility (health care utilization impact among released individuals, contributions of interagency workgroup members on outcomes); acceptability (participant satisfaction, perceived usefulness); sustainment (continued utilization), and costs req...