This large, population-based study is one of the few to examine prevalence rates of sexual harassment occurring during the past 12 months by victimization and perpetration among adolescents. In this large, cross-sectional survey of students attending 26 high schools, sexual harassment was defined using three questions from the Sexual Experiences Questionnaire. Among 18,090 students completing the survey, 30% disclosed sexual harassment victimization (37% of females, 21% of males) and 8.5% reported perpetration (5% of females, 12% of males). Sexual harassment perpetration was highly correlated with male sex, minority race/ethnicity, same-sex attraction, bullying, alcohol binge drinking, and intraparental partner violence.