Objective - Experimentation with e-cigarettes is significantly more common among 15- to 24-year-olds than in other age groups. Because e-cigarettes may contain nicotine, they could serve as a gateway to smoking. In this article, we present a review of the scientific evidence regarding the initiation or reinforcement of smoking through vaping among young people. Methods - Qualitative analysis conducted in January 2016. Articles reporting longitudinal studies conducted among adolescents and young adults exposed to e-cigarettes were selected. Results - Five articles were selected from the 544 documents identified. Of the five prospective observational studies analyzed, four concluded that there was an increased risk of initiating tobacco use among non-smoking youth exposed to e-cigarettes. The one-year probability of young adult vapers initiating tobacco use was 8.3 (95% CI = 1.2–58.6) to 12.7 (95% CI = 4.0–40.3) times higher than that of non-vapers. Having ever vaped increased the one-year risk of smoking a conventional cigarette by 75% among 14-year-old adolescents. Conclusion—Smoking initiation and continued smoking are significantly associated with e-cigarette use among adolescents and young adults. Due to methodological weaknesses, these results should be interpreted with caution. [author abstract]