This study looked at how the social constellations in school classes relate to bullying problems. Using peer-evaluation questionnaires, the peer networks of children with different participant roles (such as victim, bully, assistant of bully, reinforcer of bully, defender of victim, outsider) were explored. The subjects were 459 sixth-grade-children (218 girls, 241 boys), aged 11 to 12 years, in Finland. The main findings were: 1) Children who tended to behave in either similar or complementary participant roles in situations of bullying formed networks with each other. The individual child's behavior in bullying situations was strongly connected to how the members of his/her network behaved in such situations. 2) Bullies, assistants, and reinforcers belonged to larger networks than did defenders, outsiders and victims. 3) Children outside the networks were most often victims. It was concluded that behavior in bullying situations can be said to be one feature around which the peer networks in school classes are organized. Thus prevention, as well as intervention strategies against bullying should focus not only on individual children, but also on the wider social context of the class.