Because Conduct Disorder becomes increasingly resistant to change over time, intervention that begins in the early school years is clearly a strategic way to prevent or reduce aggressive behavior problems. Our decision to focus our interventions o n the period consisting for preschool and early school years was based on several considerations. First, evidence suggests that children with ODD and CD are clearly identifiable at this age. Second, evidence suggests that the younger the child at the time of intervention, the more positive the child's behavioral adjustment at home and at school. Third, the move to school - from preschool through the first years of elementary school - is a major transition and a period of great stress for many children and their parents. The child's early success or failure in adapting to school sets the stage not only for the child's future behavior at school and his or her relationships with teachers and peers but also for parents' future attitudes toward their child's schools and their own relationships with teachers and administrators.