PROJECT SUMMARY/ABSTRACT Approximately 1 out of every 3 adults experiencing homelessness has a current alcohol use disorder (AUD). Alcohol use plays a central role in increased morbidity and mortality in this population, with some studies suggesting it plays a direct role in as many of 17% of deaths. Alcohol is also the leading cause of homelessness and contributes to its chronicity by inhibiting progress towards obtaining employment and a stable living environment. Shelter-based treatments are common, but compliance is often poor. There are many documented challenges to effectively implementing traditional evidence-based interventions in shelter settings. Smartphone ownership and use are now widespread even among unhoused adults, with a 2017 estimate indicating that the majority own a smartphone. This number is likely to continue increasing with the availability of government subsidized smartphones and service (i.e., Lifeline program). Technical literacy and interest in technology-based interventions are similarly high. Smartphone-based treatments may offer unique benefits for this population, given the many barriers to seeking and accessing traditional treatments. The proposed project will build upon preliminary data that were collected in our recently completed NIAAA R34 study. This study identified environmental, cognitive, and behavioral antecedents to alcohol use, used this information to develop an algorithm for delivering tailored messages based on imminent drinking risk, and then conducted a pilot trial in 41 adults experiencing homelessness. Results indicated intervention feasibility and acceptability and the intervention corresponded with a 50% decrease in alcohol use from baseline. In the proposed project, we seek to scale this preliminary work by conducting a randomized controlled trial. Adults currently experiencing homelessness who report hazardous alcohol use (N = 600) will be recruited from five shelters across the Dallas, TX and Oklahoma City, OK metropolitan areas. Individuals will attend screening and training visits, then complete one week of self-monitoring (via smartphone app) before being randomized to receive either standard shelter-based treatment (Usual Care; UC), or the Smart-T Alcohol intervention + UC. The Smart-T Alcohol intervention offers on-demand content and automated contextually tailored messages to reduce alcohol consumption. The intervention period will span eight-weeks (i.e., weeks 2-9), with follow-up assessments occurring at weeks 9, 13, and 26. All participants will complete brief daily smartphone-based surveys for 13 weeks. Aims of the project will be to assess the effects of the Smart-T Alcohol intervention on alcohol use and alcohol-related problems (Aim 1), intervention effects on key drinking risk indicators and their mediation of use outcomes (Aim 2), and identify specific subpopulations (e.g., women, racial/ethnic minorities, younger adults; Exploratory Aim 3) for which the intervention is most ef...