A child's social development is rooted in opportunities, skills, and recognition that accrue through early interactions with family members, peers, teachers, neighbors, ministers, coaches, and many others. An ecological-developmental perspective focuses on opportunities for positive social participation and skills to promote building successful relationships with peers and adults who are committed to conventional lines of action. Central to the sequence of events that reinforces aggression in some families is inconsistent parental supervision of children, the use of harsh punishment, failure to set limits, neglect in rewarding prosocial behavior, and a coercive style of parent- child interaction. Aggressive behavior becomes rewarding for children in families where parents use a coercion-acquiescence style of child management. A review of social development and early aggression focuses on the social consequences of early aggression and other factors in early aggression in addition to family environment. Recent research on aggressive behavior in early adolescence is also considered. The review of the prevention of youth violence focuses on an ecological- developmental perspective, with attention to communities, families, schools, peers, and neighborhoods as the arenas in which preventive efforts must occur. This review concludes the combinations of strategies delivered across a variety of home, school, and other settings and coupled, where necessary, with substance abuse treatment have increased children's prosocial behaviors and reduced problem behavior, including both self- reports and official reports of illegal behaviors. Some characteristics of effective programs are identified. 136 references