The Olweus Bullying Prevention Program (OBPP) is a comprehensive, school-wide program that was designed in the mid-1980s to reduce bullying and achieve better peer relations among students in elementary, middle, and junior high school grades. Key program elements are described and a number of cultural adaptations to U.S. schools are noted. Several large-scale evaluations from Norway are reviewed, which provide compelling evidence of the program's effectiveness in Norwegian schools. Studies evaluating the OBPP in diverse settings in the United States are also reviewed. Although these studies have not produced completely uniform results, they have shown positive effects of the OBPP on students' self-reported involvement in bullying and antisocial behavior. Directions for ongoing and future research are noted. (Contains 1 table.)