Project Summary. The Center for the Study of Tobacco Products (CSTP) has developed a model for evaluating novel tobacco products using, as exemplars, electronic cigarettes (ECIGs) that heat a liquid that often contains nicotine, forming an aerosol that users inhale. Now, CSTP leverages its methodological and ECIG expertise to pivot from product evaluation to an integrative theme of impact analysis. Specifically, the CSTP proposes methods with which FDA can generate predictions regarding a potential regulation?s effects, and then whether or not the predicted effects occur in the population can be tested. The CSTP?s model assesses how potential regulation might influence product toxicity (Project 1), user behavior (Project 2), and product addiction/abuse liability (Project 3). Results from Projects 1-3 are used to generate predictions regarding population-level phenomena, and we test those population-level predictions using a prospective cohort survey (Project 4). Because all Projects involve manipulating ECIG device/liquid characteristics and/or collecting data from ECIG users, all would benefit from detailed and up-to-date knowledge of ECIG user behavior as well as ECIG characteristics, effects, and changing consumer and ECIG manufacturer/distributor behaviors. Because changes are rapid, this information is often difficult to attain using data from annual national surveys. In this context, the overarching goal of the Contextual Knowledge Core (CKC) is to support each project by using a combination of concept mapping and online data sources to inform Projects 1-4 so that testing conditions and data collection instruments reflect current, real-world conditions. The team?s prior studies used several methods to understand ECIG effects and user and manufacturer behavior, using strategies such as a cost- and time-efficient participatory online method known as ?concept mapping?; content analysis of a popular online video sharing site (YouTube); and systematic analyses of online forums, and manufacturer/distributor retail outlets to understand ECIG use behaviors, consumer engagement, and industry labeling practices. These studies then informed an ongoing RCT, an acute laboratory study, and work in Project 1?s aerosol research laboratory. Collectively, these methodological approaches can inform CSTP study designs, measurement instruments, and hypotheses. The CKC builds on this work and its aims are to inform Projects 1-4 using: (1) concept mapping, (2) systematic and longitudinal surveillance of online data sources like YouTube and ECIG forms, and (3) systematic and longitudinal surveillance of ECIG online retail sites. In sum, the CKC draws on the team?s proven expertise to ensure that Projects 1-4 use detailed, up- to-date information to guide device/liquid manipulations and assessment instruments. As with prior studies, the CKC will produce novel, publishable information about real-world ECIG user experience as well as user and manufacturer/distributor behavior that will inform FDA about future regulatory action.