Early intervention should begin as soon as relatively stable problem behavior is detected in young children. Once professionals have identified young children who are at risk for stable externalizing behavior problems, it is important that they use and/or recommend research-based interventions. Therefore, the first purpose of this article is to present research on specific child (e.g., temperament), family (e.g., family adversity), and transactional characteristics that have been documented to contribute to the manifestation of externalizing disorders in young children. School factors that may also support externalizing behavior in young children will also be presented and include negative teacher interactions and limited support for appropriate behavior. The second purpose of this manuscript is to present screening and intervention strategies that school psychologists could may use with young children who have externalizing behavior prior to or as soon as they enter the kindergarten setting. © 2002 Wiley Periodicals, Inc.It is important to identify young children at great risk for future behavior problems in order to initiate systematic and early interventions (Walker, 1998). Earliest possible intervention is important for these children due to their increased risk of maintaining and perhaps developing more severe behavior problems (Webster-Stratton, 1997). Research has documented that parent ratings of preschool children's behavior problems were the strongest predictor of antisocial behavior disorders at a 6-year follow-forward assessment (White, Moffitt, Earls, Robins, & Silva, 1990). Other research has similarly documented that preschool and kindergarten children with externalizing behavior were at risk for having future behavior problems and difficulty with peer relationships (Egeland, Kalkoske, Gottesman, & Erickson, 1990;Vitaro, Tremblay, Gagnon, & Biovin, 1992;Vitaro, Tremblay, Gagnon, & Pelletier, 1994). Furthermore, in a review of the research in this area, Webster-Stratton has concluded that "the primary developmental pathway for serious conduct disorders in adolescence and adulthood appears to be established in the preschool period" (p. 432).To this end it is important that professionals understand the characteristics of young children who are at risk for severe and stable externalizing behavior problems. It is also critical that professionals are aware of methods for screening young children for externalizing problems. In addition, once professionals have identified young children who are at risk for stable externalizing problems, it is important that they use and/or recommend research-based interventions.Therefore, the first purpose of this manuscript is to briefly present research on specific child (e.g., temperament), family (e.g., family adversity), and parent-child interaction characteristics that have been documented to contribute to the manifestation of externalizing disorders in young children. For more thorough reviews of this information, see Kaiser and Hester (1997), WebsterStratton (1997)...