The present study examined the effectiveness of a bullying prevention program. The responses of 270 fifth grade students on the Peer Relations Questionnaire, the Children's Depression Inventory (CDI), and the Pro-social Tendencies Scale were examined before and after participating in the program. Students in the Bully, Bully-Victim, and Neither groups had lower CDI scores than students in the Victim group, but there was not a significant change from pretest to posttest in these groups. Prosocial scores of victims and students who were neither bullies nor victims increased from pretest to posttest. In addition, the number of self-reported victims decreased and the number of self-reported bullies increased. These findings have implications for those who are developing or currently presenting bullying prevention programs. (Contains 3 tables.)