PROJECT SUMMARY Brief motivational interventions (BMIs) to reduce risky drinking in college students are well established, but the needs of emerging adult (EA) risky drinkers who live in disadvantaged communities and are not fulltime college students have been neglected. They tend to have more constrained access to rewarding opportunities, adult roles, and activities that present pro-social alternatives to heavy drinking. When coupled with the foreshortened time horizons typical of many EAs, this suggests the need for interventions that not only enhance motivation to reduce drinking, but guide EAs to engage in alternatives to heavy drinking and orient their behavior toward longer-term positive goals. Guided by behavioral economics (BE), the proposed study will disseminate and evaluate a brief motivational BE intervention that combines BMI elements with the Substance Free Activity Session shown to reduce drinking by increasing future orientation and engagement in pro-social alternatives. The intervention will be delivered using a digital platform appropriate for EAs whose social networks operate through such communications. Because peers influence substance use, a peer-driven sampling method (Respondent Driven Sampling [RDS]) will be used to recruit 500 community-dwelling EAs ages 18-28 for a cluster randomized controlled trial that compares the intervention with an educational/assessment control condition. Drinking practices and problems, BE outcome predictors, and social networks will be assessed at baseline and at 1, 6, and 12-month follow-ups. Intervention efficacy and behavior change mechanisms will be examined. Reduced alcohol demand and delay discounting and favorable post-intervention shifts in future orientation, substance-free vs. substance-involved activities, and use of protective behavioral strategies to reduce drinking-related harms are predicted to mediate intervention effects. Social network analysis will assess whether the intervention attenuates network promotion of individual drinking. The study will be the first to test a web-based alcohol reduction intervention focused on BE principles and to use digital RDS to reach community- dwelling EAs for intervention. The study will translate and test BE mediators and moderators of change, and the digital intervention has high potential for reach and scalability with under-served community risk groups.