Project 1 (P1): Use of Novel Non-Combustible Tobacco Products among US Youth (Leader, Leventhal) P1 determines how availability of different new non-combustible products impacts tobacco product use in US youth from 2024-2028. To accomplish this, P1 will: a) partner with the Monitoring the Future (MTF) Study to add a new survey module focused on tobacco regulatory science (TRS) with its own unique measures to the annual cross-sectional survey of US 8th, 10th, and 12th graders (n=221,490, pooled across years); b) test hypotheses about 5-year trends in the use of edible oral nicotine products (ONPs; gums, lozenges/mints, gummies), pouch ONPs, and e-cigarettes; c) examine the role of ONP and ecigarette product characteristics and reasons for use in ONP and e-cigarette use; and d) estimate relations of rural residence and other substance use with use and poly-use of ONPs with e-cigarettes and with combustible products. Aim 1 is to determine the epidemiology of ONP use and poly-use with e-cigarette, combustible, or smokeless tobacco in US youth, 2024-2028. We hypothesize that: (a) past 30-day use prevalence of any ONP, edible ONPs, or pouch ONPs will increase across years, (b) depressive symptoms, other substance use, and other demographics will be associated with ONP use and ONP+other product poly use. Aim 2 is to determine the role of flavors and nicotine concentration in ONP and e-cigarette use in US youth. We hypothesize that use of ONPs or e-cigarettes with: (a) concept flavors or explicitlymarketed flavors (menthol, mint, fruit, dessert, ice+fruit hybrid, non-menthol cooling) flavors vs. unflavored/tobacco flavors will be associated with higher past-30-day use frequency (1-30 days) and intensity (vaping episodes or pieces/pouches per use day); (b) nicotine concentration will have a dose-response association with use frequency and intensity. Aim 3 is to determine associations between perceived reasons for using ONPs related to product design/ characteristics and ONP use and poly-use in US youth. We hypothesize that in past-30-day ONP users: (a) citing concealability, discreetness, convenience, flavor, nicotine buzz, and use where other tobacco products are not allowed as reasons for ONP use will be associated with ONP higher use frequency and intensity; (b) citing use where tobacco products are not permitted will be associated with more frequent use of other products. Implications for Regulation: If U.S. youth use of ONPs and ecigarettes with certain flavors, nicotine concentrations, or design features (e.g., easy to conceal edible ONPs) are common and associated with frequent use and polyuse, FDA targeting of such products in marketing denials or enforcement priorities might reduce youth uptake.