PROJECT SUMMARY/ABSTRACT Tobacco control policies targeting menthol flavoring could have a significant impact on public health. When added to cigarettes, menthol increases addictive potential and dependence, leads to greater inhalation of tobacco toxicants, and decreases the likelihood of cessation. These effects are particularly felt in the African American (AA) community where targeted marketing has resulted in ≈85% of AA versus ≈20% of White smokers using menthol cigarettes. The FDA’s decision to advance the rulemaking process to ban menthol cigarettes is an important step toward closing the gap in tobacco-related disease and death disproportionately experienced by AA smokers. The agency’s regulatory action stopped short of including menthol-flavored e- cigarettes (ECs) and debate continues about whether more comprehensive enforcement priorities inclusive of menthol flavored e-liquids should be enacted. While a ban on menthol flavored EC may reduce youth and young adult initiation, it may also discourage adult menthol smokers to switch from tobacco cigarettes to EC. This could slow harm reduction and result in a negative public health impact that would be concentrated in racial/ethnic minority communities already disproportionately burdened by tobacco. FDA has identified the impact of EC flavoring on smoking patterns as a research priority area, and there is an urgent need for studies that examine possible unintended consequences of regulatory actions on tobacco-related health disparities. Our recently completed randomized clinical trial (RCT) provided menthol EC or tobacco EC to adult smokers. Among menthol smokers, we found equivalent rates of switching from tobacco cigarettes to EC, tobacco harm reduction, EC product use, and acceptability between those who used tobacco EC versus menthol EC, although the study was limited by a small sample size and was not prospectively designed for these comparisons. These data are consistent with observational studies that have found that nicotine – not flavor – drive use in adult EC users and provide strong preliminary evidence to support restrictions on menthol flavored EC given potential benefit to youth and lack of evidence of harm to adult smokers. However, a prospectively designed and fully powered RCT is needed to empirically answer this question. The objective of this application is to provide much needed data to the FDA to guide regulatory action on EC flavoring. Menthol smokers (n=800), stratified by race and gender, who are interested in switching to EC, will be randomized 1:1 into a 12-week open label, non-inferiority RCT comparing menthol EC versus tobacco EC. Follow-up will continue through week 26. The central hypothesis is that tobacco EC are not inferior to menthol EC at facilitating a switch to EC in menthol cigarette smokers. We further hypothesize no difference in tobacco harm reduction, EC product use, or acceptability between participants randomized to tobacco EC versus menthol EC. T...