Bullying involves a powerful person intentionally harming a less powerful person repeatedly. With advances in technology, students are finding new methods of bullying, including sending harassing emails, instant messages, text messages, and personal pictures to others. Although school bullying has been studied since the 1970s, relatively little is known about students' experiences of cyberbullying. The present study explored the prevalence of cyberbullying while also examining sex and grade differences. Results showed that a substantial proportion of students in Grades 6, 7, 10, and 11 are involved in cyberbullying: Girls are more likely than boys to be the targets of cyberbullying, and cyberbullying declines in high school. Despite significant findings, the magnitude of these group differences is small. Implications for interventions are discussed. (Contains 4 tables.)