Russia and Eastern Europe continue to have one of the fastest growing HIV epidemics in the world, with highest transmission risks among people who inject drugs (PWID) and their sexual partners. While routine HIV testing within addiction treatment systems in Russia (i.e., narcology hospitals) is the norm, links between the narcology and HIV care systems are limited and ineffective. In St. Petersburg 50-60% of PWID are HIV- infected, yet among this population less than 10% are on antiretroviral therapy (ART). For Russia to make progress toward the UNAIDS 90-90-90 targets (i.e., 90% aware of HIV diagnosis, 90% of those diagnosed on ART and 90% of those on ART with suppressed HIV viral load [HVL]), a bold new strategy is required. The objective of this study, ?Linking Infectious and Narcology Care ? Part II (LINC-II),? is to implement and evaluate, via a two-armed randomized controlled trial among 240 HIV-infected PWID, a multi-faceted intervention combining pharmacological therapy (i.e., rapid access to ART and receipt of naltrexone for opioid use disorder) and 12 months of strengths-based case management. The central hypothesis is that LINC-II will lead to marked progress toward the achievement of the 90-90-90 HIV cascade of care targets among HIV- infected PWID, relative to current standard of care, and that LINC-II will facilitate health system coordination of narcology and HIV care. The rationale that underlies this proposal emerged from the original LINC study (R01DA032082), which found 6 months of case management to be effective for improving linkage of HIV- infected PWID to HIV care, but was unable to effect change in HVL, CD4, or retention in care due to complex processes for ART access, active substance use, and inadequate length of the CM intervention. LINC-II aims to: 1) evaluate the effectiveness of LINC-II on undetectable HVL at 12 months (primary outcome), initiation of ART within 28 days of randomization, change in CD4 count from baseline to 12 months, retention in HIV care (i.e., ? 1 visit to medical care in 2 consecutive 6 month periods), and undetectable HVL at 6 months; 2) evaluate the impact of LINC-II on coordinated care across the narcology and HIV health care systems, using mixed methods data from health care providers, administrators, and patients; and 3) evaluate the cost- effectiveness of the intervention to inform policy makers on scaling up the LINC-II approach both within Russia and other countries with HIV epidemics driven by injection drug use. The study's goal is to improve upon current seek, test, treat, and retain efforts for HIV-infected Russian PWID in narcology care, a group routinely tested for HIV. The LINC-II study will be undertaken by an international research team uniquely experienced in addressing HIV, substance use, and clinical interventions in Russia. If LINC-II is effective and can be embedded efficiently within the Russian and other medical systems challenged by HIV-infected PWID, then it has great potential to favorably impact the HIV epidemic in a key HIV population.