This project will assess the ways in which e-cigarette product diversity impacts the user experience to inform potential regulations by identifying product characteristics that may: (1) put young adults at risk for tobacco product use; and (2) facilitate adult smokers switching to e-cigarettes. There are three primary objectives to the study: (1) Determine which dimensions of e-cigarette product diversity differentially affect product appeal in the overall population of tobacco product users as well as affect product appeal across young adult e-cigarette users and middle-age/older adult smokers; (2) Determine which dimensions of e-cigarette product diversity differentially affect product appeal in the overall population of tobacco product users as well as affect abuse liability in young adult e-cigarette users and the ability to resist smoking in adult smokers; (3) Determine the affect of product characteristics on e-cigarette nicotine delivery profile. For this substudy, adult smokers (N=200) will attend two laboratory session in which they will self-administer e-cigarette products varied according to within-subject e-cigarette factors (e.g., flavor, nicotine formulation) and smoke their own cigarettes.

Inclusion Criteria:

• Regular use of cigarettes containing nicotine.

Exclusion Criteria:

• Pregnant or planning to become pregnant.