In investigating what is known about effective interventions to prevent physical aggression and violence, five rules on implementing an intervention are proposed: (1) the importance of rigorous evaluation; (2) seek to prevent rather than to intervene and do it early in a child’s life; (3) intervene in multiple domains of the child’s life; (4) pay attention to treatment fidelity when implementing programs and the need for quality trained professionals; and (5) development of substantive guidelines and recommendations of specific prevention programs. In addition, seven possible prevention strategies are examined that have been evaluated. They include: (1) promote the physical health of mother and child; (2) increase income; (3) home visiting; (4) childcare; (5) preschool; (6) improve parenting skills; and (7) increase access to existing services. The review indicates that preventive programs constitute a good strategy for the healthy development of children. They also carry with them the possibility of impacting upon a broad range of social ills. However, a recommendation is made that policymakers seek out rigorous research to help formulate their preventive policies so as to implement the most effective programs. An extensive review of literature indicates that the best way to limit aggressive behavior is to work on preventing it before the pattern is established in the child. In other words, policies should support programs that look to prevent rather than waiting to intervene. The premise of this paper is that physical aggression can be successfully influenced, but that there is a small window of opportunity in which to do this. References