Electronic nicotine delivery systems (ENDS) have been gaining in popularity. The few prevalence studies in adults have found that most ENDS users are current or former smokers. The objectives of this study were to estimate the prevalence of ENDS usage in adolescents, and examine the correlates of use. Self-administered written surveys assessing tobacco use behaviors were conducted in multiple waves as part of a larger intervention study in two large suburban high schools. The prevalence of past-30 day ENDS use increased from 0.9% in February 2010 to 2.3% in June 2011 (p=0.009). Current cigarette smokers had increased odds of past-30 day ENDS use in all study waves. When adjusted for school, grade, sex, race and smoking status, students in October 2010 (Adjusted OR 2.12; 95% confidence interval (CI): 1.12-4.02) and June 2011 (Adjusted OR 2.51; 95% CI: 1.17-4.71) had increased odds past-30 day ENDS use compared to February 2010. The prevalence of ENDS use doubled in this sample of high school students, and current cigarette smoking is the strongest predictor of current use. Continued monitoring of ENDS is needed to determine whether it increases the likelihood of cigarette smoking initiation and maintenance in youth.