High-intensity drinking — e.g., consuming 10 or 15 or more drinks in a row — has recently been acknowledged as a serious health problem among young adults that requires urgent research attention. Our previous work (R01AA023504) documented prevalence, predictors, and developmental change in high-intensity drinking from ages 18 to 30 through secondary data analysis of the national Monitoring the Future (MTF) study. Alcohol use, in general, and 5+ and 10+ drinking, in particular, reach lifetime peaks in the early-to-mid 20s; therefore, understanding the patterns, predictors, and consequences of high-intensity drinking across the transition to adulthood is especially critical. A better understanding of the situational predictors and short- and long-term consequences of high-intensity drinking is needed to understand the motives, contexts, and public health impacts of high-intensity drinking. Building on our previous findings using biennial data from the MTF study, the current application is to conduct primary data collection from a national sample of high school students. High school students (modal age 18; N=2000) who participate in MTF school-based surveys in 2018 (and who are not selected for the MTF biennial young adult surveys) will be sampled for a 4-year web-based measurement burst study across the transition into young adulthood. Annual data collection bursts (14 consecutive days of daily surveys per year) will be conducted at modal ages 19, 20, 21, and 22. Specific aims are to examine: (1) occasion-level predictors (e.g., affect, motives, contexts of drinking) and developmental predictors (e.g., age, social role status) of high-intensity drinking; (2) occasion-level consequences (e.g., blackouts, aggression) associated with high-intensity drinking; and (3) age-specific and longitudinal patterns of high-intensity drinking and drinking consequences during the transition into young adulthood (ages 18-22). For each aim, we will also examine variation based on developmental and sociodemographic indicators. The project will be the first national study of both college attenders and non-attenders to identify predictors (e.g., affect, motives for drinking, drinking contexts, and other substance use that day) and consequences (e.g., blackouts, injury, aggressive behavior, sexual risk, and negative interpersonal consequences) of specific occasions of high-intensity drinking, and will provide critical information for health promotion and intervention efforts targeting high-risk alcohol behaviors among young adults.