The Affordable Care Act (ACA) allows insurers to charge tobacco users who have nongroup coverage up to 50 percent more than nonusers of tobacco. In this study we used 2014-19 administrative data on enrollees in the federally facilitated ACA Marketplace, HealthCare.gov, to examine the relationships among surcharge rates, total Marketplace enrollment, and enrollment by tobacco users. We found that the tobacco surcharge rate averaged approximately 14 percent and that it was associated with lower total enrollment as well as a reduced share of total enrollees who reported any tobacco use. Our analysis also found that tobacco surcharges have a significantly larger effect on tobacco users' share of enrollment in rural areas than in urban areas, which may in turn contribute to urban-rural health disparities. Given that tobacco surcharges may decrease Marketplace enrollment overall and shift the composition of enrollment away from tobacco users, our findings suggest that reducing tobacco surcharges may increase total Marketplace enrollment.