E-cigarettes have been suggested as a strategy for reducing harm from cigarettes. Although e-cigarettes could be a less-harmful alternative to cigarettes for those trying to quit, there may also be costs that outweigh any benefits of reduction. The purpose of the present study was to prospectively investigate perceptions of e-cigarettes, cigarette smoking intentions, and their associations with e-cigarette use over time. Community participants (N = 348, 57% male) aged 18 to 24 years were recruited for a longitudinal study of tobacco use. Inclusion criteria included nondaily cigarette smoking for ≥ 6 months with no history of daily smoking. Participants reported e-cigarette use over the past 14 days at baseline, and for the past 9 days at 3, 6, and 9 months. Assessments were completed online or via mobile phone. Across the 4 assessments, 22% to 33% of participants reported recent e-cigarette use. Intent to quit smoking cigarettes and intent to maintain smoking were unrelated to e-cigarette frequency. E-cigarette frequency was positively associated with perceiving e-cigarettes as less harmful than cigarettes and more positive e-cigarette expectancies (ps < .05). E-cigarette use was also more frequent among those who smoked cigarettes frequently and who used e-cigarettes to circumvent cigarette bans more often (ps < .05). The combination of these findings suggests that, at least among nondaily smoking young adults, other factors may influence frequency of e-cigarette use more than harm reduction. Findings instead seem consistent with the hypothesis that e-cigarettes are more often used to complement ongoing cigarette smoking.