PROJECT SUMMARY/ABSTRACT Electronic nicotine delivery systems (ENDS) have emerged in the US market, with use and awareness rapidly increasing in recent years, particularly in young adults. While ENDS may facilitate harm reduction in smokers, ENDS represent significant health risks (e.g., addiction in young adults). From a socioecologic perspective, the literature regarding tobacco retail indicates that place characteristics such as neighborhood demography and policy context influence retailer location and marketing, and these factors impact individual tobacco use. However, this literature is in its infancy in regard to ENDS and particularly to vape shops, which are stores exclusively devoted to ENDS sales. Vape shops have proliferated in the US and are unique in their product offerings, marketing, and overall retail environment. A particularly important and timely macro-level factor that may impact ENDS use and distribution channels is FDA Deeming Regulation, which will impact vape shops, their marketing, and young adult ENDS use. Leveraging a Socioecological Framework, the parent R01 draw’s data from 6 metropolitan statistical areas (MSAs) representing the gradient of tobacco control in order to address 3 inter-related aims: 1) examine density and survival of vape shops over time and across contexts in relation to FDA regulation, local policies, and other sociocontextual factors (e.g., neighborhood context, density/proximity of convenience stores); 2) examine vape shop marketing and POS practices (e.g., age verification, free sampling, health warnings) over time and across contexts in relation to FDA regulation, local policies, and other sociocontextual factors (e.g., neighborhood context, density/proximity of convenience stores); and 3) examine young adult ENDS use over time and across contexts in relation to spatial access to vape shops and convenience stores, ENDS advertising exposure, local policies, and sociocontextual factors. If funded, this Diversity Supplement will provide Dr. Daisy Le with unique training, mentorship, and research experiences to further establish her research career in cancer-related health disparities. Specifically, Dr. Le will capitalize on the vast data collected on the cohort of 3006 young adults across the MSAs and establish the foundation for ENDS cessation research by conducting formative research and message testing. We will disseminate findings with an explicit focus on informing public health policy and practice regarding ENDS, as well as future research.