Cyberbullying perpetration (using communication technology to engage in bullying) is a recent phenomenon that has generated much concern. There are few prospective longitudinal studies of cyberbullying. The current article examines the individual, peer, family, and school risk factors for both cyber and traditional bullying (the latter is bullying that does not use technology) in adolescents.This article draws on a rich data set from the International Youth Development Study, a longitudinal study of students in Victoria, Australia and Washington State, United States, which began in 2002. In this article, data from almost 700 Victorian students recruited in grade 5 are analyzed to examine grade 7 (aged 12-13 years) predictors of traditional and cyberbullying perpetration in grade 9 (aged 14-15 years).Fifteen per cent of students engaged in cyberbullying, 21% in traditional bullying, and 7% in both. There are similarities and important differences in the predictors of cyber and traditional bullying. In the fully adjusted model, only prior engagement in relational aggression (a covert form of bullying, such as spreading rumors about another student) predicted cyberbullying perpetration. For traditional bullying, previous relational aggression was also predictive, as was having been a victim and perpetrator of traditional bullying, family conflict, and academic failure.The use of evidence-based bullying prevention programs is supported to reduce experiences of all forms of bullying perpetration (cyber, traditional, and relational aggression). In addition, for traditional bullying perpetration, addressing family conflict and student academic support are also important.