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 across young adult e-cigarette users and middle-age/older adult smokers with an interest in, but no significant experience with, e-cigarettes; (2) Determine which dimensions of e-cigarette product diversity differentially affect abuse liability in young adult e-cigarette users and the ability to resist smoking in adult smokers with an interest in, but no significant experience with, e-cigarettes; (3) Determine the affect of product characteristics on e-cigarette nicotine delivery profile. For Aim 1, young adult vapers (N=200) and adult smokers (N=200) will attend one laboratory session in which they will self-administer e-cigarette products varied according to within-subject e-cigarette factors (e.g., flavor, pg/vg ratio). For Aim 2, young adults vapers (N=360) and adult smokers (N=360) will administer an e-cigarette product and complete behavioral economic tasks that test the participant's choice of earning money to delay initiation and continued use of: (1) The sampled e-cigarette product (abuse liability; young adult vapers); or (2) Their own brand cigarettes (ability to resist smoking; adult current smokers). A pilot study will establish device and e-liquid parameters (e.g., nicotine concentration) to be used for all aims.

Inclusion Criteria:

Vapers

1. E-cigarette use >3 day/week for >2 months
2. Report regularly using e-cigarette products with nicotine
3. Positive cotinine test via NicAlert test strip

Smokers

1. Daily cigarette smoking for ≥ 2 years
2. Currently smoke > 4 cig/day
3. Interest in trying an e-cigarette or current use of e-cigarettes

Exclusion Criteria:

Vapers

1. Pregnancy/breastfeeding
2. Desire to immediately reduce e-cigarette use

Smokers

1. Breath CO < 9ppm at intake
2. Pregnancy / breastfeeding
3. Current daily use of other combustible tobacco products (e.g., cigars)