PROJECT SUMMARY Many young adults engage in heavy drinking and in turn experience negative consequences (e.g., severe injury, overdose). While personalized feedback interventions (PFIs) show promise among college students, non- college young adults are often excluded from research, effect sizes tend to be small to medium, gains are not usually maintained, and improvements in engagement and potential for reach are needed. Mobile technology can be harnessed to deliver intervention, but many mHealth platforms are not theoretically based or rigorously developed and tested. Preliminary work suggests that the morning after drinking may represent a “teachable moment” not yet exploited for harm reduction. We propose to examine mornings after drinking as an optimal time to provide repeated, personalized feedback with the goal of reducing hazardous drinking. Specifically, we will further develop and pilot test a novel theory-based PFI for heavy drinking young adults. Innovations include mobile delivery of feedback in multiple doses that occur close in time to drinking; choice of feedback; feedback informed by daily, mobile assessment of recent key drinking events; and use of personalized and dynamic goal setting to guide behavior change. In line with principles of the transtheoretical model (e.g., developing discrepancy), intervention strategies include personalized feedback (e.g., prior night blood alcohol concentration, consequences) contrasted with both drinking goals set at baseline and corrective normative feedback (e.g., how last night’s drinking compares to peers). We have promising preliminary data on this intervention; however, prior pilot participants included only college students. Further, they were paid for compliance with the daily surveys that informed their feedback, but engagement in the absence of monetary reward is essential to scalability. In the proposed study, we will incorporate end-user feedback on ways to increase engagement, and manipulate payment in order to determine engagement with a more scalable (i.e., unpaid) daily PFI. First, a refined version of our mobile daily PFI will be delivered in an open trial to 20 heavy drinking young adults (50% non-college). After four weeks of daily intervention, participants will return for individual interviews to inform further refinement of the intervention content. Finally, 132 participants (50% non-college) will be randomized to one of three groups: PFI with monetary incentives for daily surveys, PFI without monetary incentives, or survey assessment only. We will examine recruitment rates, retention rates, confirmation of intervention content delivery/intake, response rates to daily surveys, data quality, and ratings of intervention value. We will test whether these indicators of engagement differ between those who do and do not receive monetary incentives for daily surveys. Further, baseline, post-test, and 3-month follow-up assessments will allow us to estimate effect sizes for PFI vs c...