RecruitingClinical trialThe Role of Flavor in the Substitutability of E-cigarettes for Combustible Cigarettes Among Persistent SmokersThis between-subjects study aims to evaluate the effect of flavor on initial and sustained switching from combustible cigarettes to e-cigarettes among 210 cigarette smokers. After measuring baseline cigarette smoking rate, participants will be randomized to a six-week regimen of fruit-flavored, tobacco-flavored, or menthol-flavored e-cigarettes and be instructed to switch (versus smoking cigarettes) over a 6-week period. Flavor-associated subjective reward and the reinforcing value of flavored e-cigarettes relative to combustible cigarettes will be assessed as mechanisms.