Bullying in schools is a serious and prevalent problem. Research conducted around the world has established the negative impact of bullying on both children who are bullied and those who bully others. Until recently, research on bullying in American schools lagged behind work done in other countries. However, increasing attention and concern has put the problem of bullying at the center of public policy. State legislatures have recently begun to mandate that schools take active steps to reduce bullying. Here we summarize the research literature on bullying, including its prevalence and impacts, and features of effective school-based interventions.