This large, statewide sample from 26 high schools provided the first population-based estimates of stalking victimization and perpetration among adolescent females and males. Our stalking definition required that pursuing tactics occurred at least 3 times in the past 12 months and included being followed, spied on, or monitored; someone showed up or waited for you when you did not want them to; and receiving unwanted messages. Among 18,013 students, 16.5% disclosed being stalked and 5.3% stalking; 2.8% disclosed both stalking victimization and perpetration. A majority of students reported being most afraid of a former boyfriend or girlfriend as the stalker.