PROJECT SUMMARY/ABSTRACT E-cigarettes, or electronic nicotine delivery systems (ENDS), are the most frequent tobacco product used by adolescents (As, aged 14-17) and young adults (YAs, aged 18-24). While growing evidence suggests ENDS as a possible strategy for smoking cessation among established adult smokers, the majority of A/YAs report never smoking cigarettes. This population needs evidence-based treatment to quit ENDS and avoid life-long nicotine addiction and the potential health harms associated with use. To date, there has been only one randomized controlled trial on e-cigarette cessation which used the texting program, This is Quitting, to help YA ENDS users quit. Our goal is to improve understanding of how to help A/YA ENDS users quit and ultimately increase cessation rates. This career development proposal is designed to increase our understanding of how to: a) promote A/YA engagement with ENDS cessation programs; and b) help A/YA ENDS users successfully quit while providing the training, experience, and data necessary to become an independent physician scientist focused on designing, implementing, and assessing A/YA ENDS cessation interventions. The specific AIMS of this K08 proposal are to: 1) Identify predictors of A/YA ENDS quit attempts (Aim 1a) and cessation success (Aim 1b), in a nationally representative sample, 2) Examine A/YA perspectives on strategies to increase engagement with, This is Quitting, with a focus on how to operationalize financial incentives to promote engagement, and 3) Evaluate the feasibility, acceptability, and preliminary efficacy of two enhancements to This is Quitting (financial incentives and NRT), on engagement and ENDS cessation success in YA users. This proposal is based at the UW-Center for Tobacco Research and Intervention and supported by an expert team of mentors and collaborators who represent leaders in tobacco research, qualitative research, data analysis, and clinical trials. This group, along with my education program, will help guide the achievement of the following training objectives: (1) advance knowledge and skills in experimental design, implementation, and evaluation (2) advance understanding of qualitative methodology (3) Increase knowledge of nicotine addiction treatment via both medication and psychosocial interventions, and (4) gain a better understanding of research ethics, leadership, and skills in manuscript and grant writing. Combined, this research proposal and education plan can improve our understanding of how A/YA ENDS users can quit and prepare me with the knowledge to use those findings to apply for a more definitive treatment study to help A/YA ENDS users quit.