This article describes the development and evaluation of a bullying prevention program in one large, public elementary school. The program, which was developed based on a collaborative model between school personnel and university consultants, included modification of the school environment, education of students, and training of teachers. To evaluate the program, all students completed an anonymous survey in the spring of 1998 (n = 541) and the spring of 1999 (n = 520). Among the younger children, a 40% reduction in the mean self-reported aggression and a 19% reduction in mean self-reported victimization were found. Among children in third through fifth grade, a 23% reduction in the mean reported victimization was observed, but no significant differences in aggression were found. This article proposes a model of translating theory and research of violence prevention into action.