PROJECT SUMMARY/ABSTRACT While tobacco smoking has declined dramatically among adolescents and is now almost rare, the prevalence of electronic nicotine delivery device (ENDS, nicotine vaping) use has risen rapidly, fueled by social media promotion, innovative product engineering, and advertising, and effectively reversing five decades of progress in youth tobacco control. The increase in high school vaping from 2017-18 was the largest one-year increase in any substance used over the 44 years that Monitoring the Future has tracked adolescent substance use. In 2019, 26% of U.S. high school seniors reported past month vaping, a 5% increase from 2018, with the sharpest inflection in vaping initiation at around age 16. Most youth who initiate ENDS use have never smoked tobacco; however, nicotine vaping is associated with subsequent initiation of tobacco smoking. This is of high public health importance because high school aged adolescents are in the developmental period with the highest lifetime vulnerability for drug use to progress to entrenched addictive patterns. Thus ENDS use puts adolescents at high risk for nicotine addiction, escalation to entrenched combusted tobacco, multiple tobacco product, and other drug addiction, in addition to negative health effects of vapor exposure. Recent surveys indicate that over half of adolescents who vape nicotine want to quit, but there are no known effective treatments to aid the millions of U.S. adolescents who have begun to vape nicotine to quit. There is growing consensus that effective interventions are needed for adolescents with pre-addiction, operationalized as mild to moderate substance use disorder, with the rationale that early interventions could prevent escalation to often lifelong patterns of drug use. Thus, here we propose to enroll adolescents with at least once weekly vaping in the past month, whose mild severity of use would exclude them from most cessation clinical trials. Because vaping has become so prevalent in high schools at a time of unprecedented behavioral health workforce shortage, effective interventions that are scalable into school and community settings are needed. We designed QuitVaping to be a fully remote, digital and behavioral intervention, grounded in Cognitive Behavioral, Social Cognitive and Dissonance Theory to be developmentally appropriate for mid and late adolescent tobacco vaping cessation. QuitVaping is delivered over twelve 20-minute sessions by young adult lay counselors. QuitVaping has high satisfaction ratings, retention, and abstinence rates in preliminary testing in adolescents with established nicotine dependence. Here we propose to test QuitVaping to promote nicotine vaping cessation in youth who vape as little as at least once a weekly, and thus are at risk for progression along the spectrum of addictive disorders, with no, mild or moderate dependence on vaped nicotine, thus meeting criteria for pre-addiction. To maximize generalizability, the trial will...