Project 2 examines the role of oral nicotine products (ONPs) and e-cigarettes in adverse longitudinal AYA tobacco product use outcomes, and the product characteristics and populations driving these outcomes. To accomplish this, P2 will: a) extend semi-annual surveys in an ongoing prospective cohort of adolescents (n=2,619) into young adulthood; b) establish a new adolescent cohort (n=2,500) who will be surveyed semiannually from age 14-18. In both cohorts, surveys will measure patterns and product characteristics of ONPs, e-cigarettes, and other tobacco products used at each wave, supplemented with a novel discrete choice task that will assess implicit preferences for ONPs and e-cigarettes in various flavors and nicotine concentrations. Aim 1 is to determine whether ONP use is associated with subsequent risk of ecigarette and combustible tobacco use initiation and escalation among AYAs. We hypothesize that ONP use frequency will predict subsequent e-cigarette and combustible tobacco use: (a) initiation, (b) frequency, and (c) intensity. Aim 2 is to identify the product characteristics of novel ONPs and e-cigarettes that increase risk for AYA use escalation and dependence symptoms. We hypothesize that risk of progression in AYA ONP and e-cigarette use frequency and intensity, and dependence symptom levels will be higher in AYAs who use and have implicit preferences for ONPs and e-cigarettes with the following characteristics: (a) very high vs. high or low nicotine concentrations; (b) ambiguously-named concept flavors, explicitly-named fruit, menthol, mint, or ice+fruit hybrid flavors vs. unflavored products or tobacco flavors; and (c) designs that promote more discrete use. Aim 3 is to explore differential patterns of ONP initiation, use escalation, and poly-product use across population characteristics. Implications for regulation: If we find that certain product classes, product characteristics, or populations are associated with adverse longitudinal nicotine use outcomes in AYAs, targeting these products in regulatory restrictions (e.g., marketing denials, enforcement) may yield benefits. Namely, such regulations could deter AYAs who start using non-combustible products from progressing toward more adverse patterns of use.