As access to technology is increasing in children and adolescents, there are growing concerns over the dangers of cyber bullying. It remains unclear what cyber bullying looks like among young Canadian children and how common these experiences are. In this study, we examine the psychometric properties of a measure of cyber bullying behaviors and victimization experiences. We also examine the frequency of these behaviors and experiences among fifth-and sixth-grade Canadian children at the beginning (n = 714) and end (n = 638) of a school year. Children's cyber bullying behaviors and victimization experiences were relatively stable across the school year and were highest for sixth-grade students who reported greater access to and use of technology. Cyber bullying behaviors representing joking around were endorsed more frequently than aggressive types of behaviors (i.e., spreading rumours or posting embarrassing pictures online). Implications for school-based prevention efforts are discussed.