PROJECT SUMMARY/ABSTRACT Polysubstance use involving opioids and methamphetamine is emerging as a new public health crisis. Patients with opioids and methamphetamine use often experience serious medical complications requiring hospitalization, which provides an opportunity to offer addiction treatment. Prior research demonstrated the feasibility and efficacy of initiating buprenorphine among hospitalized patients with opioid use disorder (OUD). Yet linkage to outpatient treatment post-discharge is suboptimal and methamphetamine exacerbates outcomes: our research showed that people with OUD who use methamphetamine have 40% lower rates of treatment linkage and are 2.4 times more likely to discharge from outpatient buprenorphine treatment programs. Building upon the prior studies, we propose to develop an intervention for hospitalized patients with OUD and methamphetamine use that combines the flexibility and human connection of patient navigation (PN) with the efficacy and scalability of mHealth-based financial incentives for linkage and medication adherence. Guided by the Information-Motivation-Behavioral Skills (IMB) Model, we propose to pilot test “MHealth Incentivized Adherence Plus Patient Navigation” (MIAPP) to promote treatment linkage and retention for patients with OUD and methamphetamine use who initiate buprenorphine in the hospital. To our knowledge, this will be the first research to examine the benefits of a combined PN/mHealth approach to improve care transitions for hospitalized patients with opioid and methamphetamine use. Our Aim #1 is to perform a two- arm, pilot randomized clinical trial (n=40) comparing MIAPP + treatment-as-usual (TAU) versus TAU alone on outpatient MOUD linkage within 30 days (primary) and 90-day retention on medications (secondary) among hospitalized patients with OUD and methamphetamine use. Our Aim #2 is to develop health services outcome measures by performing a retrospective, observational study of hospitalized patients initiated on buprenorphine from 2019–2021 to 1) describe healthcare utilization outcomes (ED visits and hospital readmission) at 30, 90 and 180 days and 2) examine associations between baseline methamphetamine use and healthcare utilization. This pilot will provide preliminary evidence of feasibility for a subsequent R01 study to test the effectiveness of the intervention. If shown to be effective, this PN+mHealth approach could provide a transformative service model that helps reduce substantial gaps in MOUD initiation and retention for persons with opioid and methamphetamine use.