This study examined the prevalence of bullying and victimization among Canadian school children. Using a questionnaire developed by Olweus, the study surveyed 4,743 children in grades 1 through 8. Six percent of children acknowledged bullying others "more than once or twice" in the preceding 6 weeks, and 15 percent of children reported they had been victimized at the same rate. Very few (2 percent) reported being both bullies and victims. Fourteen percent of children reported being bullied because of their race. There were significant developmental differences. With increasing age, there was an increase in the tendency to join in bullying, a decrease in willingness to help a victim, and a decrease in reports of peers assisting victims. Bullies were more likely to be known to teachers, and victims were more likely to be known to parents. The findings pose implications for intervention efforts to reduce bullying in schools. (Contains 11 references.) (EV)