The 44 program evaluations that met the criteria for the meta-analysis showed that school-based anti-bullying programs are effective in reducing bullying perpetration and victimization (being bullied). On average, the programs decreased bullying by 20 percent and decreased bullying victimization by 17-20 percent. The effects were generally greatest in the age-cohort designs and lowest in the randomized experiments; however, it was not clear that the random experiments were methodologically superior in all cases. The main policy implication of this review is that new anti-bullying programs should be designed and tested based on the key program elements and evaluation components found to be most effective. The authors advise that now is an appropriate time to mount a new long-term research strategy that examines the effectiveness of anti-bullying programs. The authors further recommend that a system of accrediting anti-bullying programs should be developed under the supervision of an international body such as the International Observatory on Violence in Schools. This review went beyond previous reviews by doing more extensive searches for evaluations. Of the 53 different program evaluations analyzed, only 44 provided data that permitted the calculation of an effect size for bullying or victimization. Studies were included in the review if they evaluated the effects of an anti-bullying program by comparing an experimental group that received the intervention with a control group that did not. 14 tables, 7 figures, and 165 references