Imagine that you are entering a school yard during break time. Almost all children are playing together except Anna. Peter is making fun of Anna and does not want her to join. Peter is perceived as very popular in the school. Unsurprisingly, some classmates assist Peter in this bullying behavior by calling Anna names and others provide him with an audience by laughing at her. There is a small group of children who do not take sides with either Anna or Peter. Luckily, Laura, who is relatively popular and well-liked, stands up against the bullying by telling Peter to stop his behavior and by reporting the incident to the teacher. Peter is angry at Laura, but he and his friends go away after her intervention. Anna feels better after Laura's intervention.This everyday example of bullying at school shows that bullying is not limited to a bully harassing a victim but relies strongly on peers and group processes. Peers can affect both the prevalence and the consequences of bullying. This influence of peers in bullying occurs at different levels: First, in the behavior they adopt in bullying situationsalso referred to as participant roles. Peers of bullies and victims can be assistants, who join the ringleader bully in attacking the victim; reinforcers, who provide an audience and laugh at the victim without being actively involved in the bullying; defenders, who intervene to try and stop the bullying, tell the teacher about it, and comfort the victim; or outsiders, who do not take sides with either the bully or the victim (Salmivalli, Lagerspetz, Björkqvist, Österman, & Kaukiainen, 1996). Second, the status that peers accord to their classmates -either by liking them or finding them popular -can influence bullying behavior and all other bullying-related behaviors. Third, characteristics of the classroom peer network as a whole, such as classroom social norms or the degree of hierarchical organization among classmates, can deter or facilitate bullying and might moderate its effects on victims.