Aims: We estimate associations between e-cigarette prices (both disposable and refill) and e-cigarette use among middle and high school students in the United States. We also estimate associations between cigarette prices and e-cigarette use. Design: We use regression models to estimate the associations between e-cigarette and cigarette prices and e-cigarette use. In our regression models, we exploit changes in e-cigarette and cigarette prices across four periods of time and across 50 markets. We report the associations as price elasticities. In our primary model, we control for socio-demographic characteristics, cigarette prices, tobacco control policies, market fixed effects, and year-quarter fixed effects. Setting: United States of America. Participants: 24,370 middle and high school students participating in the Monitoring the Future Survey in years 2014 and 2015. Measurements: Self-reported e-cigarette use over the last 30 days. Average quarterly cigarette prices, e-cigarette disposable prices, and e-cigarette refill prices were constructed from Nielsen retail data (inclusive of excise taxes) for 50 U.S. markets. Findings: In a model with market fixed effects, we estimate that a 10% increase in e-cigarette disposable prices is associated with a reduction in the number of days vaping among e-cigarette users by approximately 9.7% (95% CI = -17.7% to 1.8%; p=0.02) and is associated with a reduction in the number of days vaping by the full sample by approximately 17.9% (95% CI=-31.5% to -4.2%; p=0.01). Refill e-cigarette prices were not statistically significant predictors of vaping. Cigarette prices were not significantly associated with e-cigarette use regardless of the e-cigarette price used. However, in a model without market fixed effects, cigarette prices were a statistically significant positive predictor of total e-cigarette use. Conclusions: Higher e-cigarette disposable prices appear to be associated with reduced e-cigarette use among adolescents in the US.