Alcohol is the most prevalent psychoactive substance used by college students and is associated with a variety of short- and long-term negative consequences. Although many students experience negative consequences, some continue to drink at problematic levels. The present proposal extends a program of research focused on understanding daily process models of alcohol expectancies, alcohol use, and related consequences among college students. Our prior work (R01AA016979, PI Lee) examined how expectancies influence drinking and consequences later that day, how learning might take place when examining the influence of consequences on future expectations of alcohol?s effects, and for whom these relationships exist. We collected data three times a day for two weeks in each of four quarters across one year. We found significant day-to-day variability in positive and negative alcohol expectancies and resulting alcohol use and consequences, as well as important links between daily alcohol expectancies and next-day high-risk alcohol use and between daily consequences and next-day expectancies. Overall, findings have important implications for timing intervention delivery to target daily expectancies. The present proposal tests an intervention with real-time feedback using individuals? daily expectancies, use, and consequences, and builds on prior NIAAA Tier 1 strategies for addressing high-risk college student drinking by focusing on challenging alcohol-related social expectancies through in-vivo experimental designs. Drawbacks of in-vivo alcohol expectancy challenge (AEC) interventions include low utilization due to lack of feasibility for widespread implementation. Therefore, the present competing renewal application will design a mobile phone application for data collection and intervention. This mobile AEC (mAEC) intervention is designed to challenge daily-level alcohol expectancies and reduce high-risk drinking and negative consequences. We will incorporate relevant adapted components of previous AEC approaches in combination with methods and results from our prior R01 to develop mAEC, which will be implemented daily across 14-days with follow-ups up to 12-months. The mAEC will provide individualized, daily feedback based on students? drinking intentions, alcohol expectancies, and consequences. A sample of 450 high-risk college drinkers will be recruited and randomized to one of two conditions to compare the efficacy of the mAEC and assessment-only control conditions. Specific aims are to examine the efficacy of the mAEC intervention, expectancies as mediators of intervention efficacy, and whether the intervention weakens the daily link between positive expectancies and consequences and strengthens the daily link between negative expectancies and consequences. The mAEC intervention has the potential to have a major impact on the field of alcohol intervention because it will be scalable and easily disseminated given its use of mobile technology and empirically-supported approach that targets individuals? alcohol expectancies and capitalizes on daily variability in expectancies and drinking.