Multiple gating, which is considered to be a cost-effective screening method for identification of children at risk of developing serious antisocial behaviors, uses relatively inexpensive ratings as a first gate and more sophisticated assessments in the following steps. Different assessment strategies were tested to find a combination of predictors at the beginning of elementary school that could effectively identify children who are at risk of developing serious antisocial problems. All boys in 54 schools, located in low socioeconomic districts in montreal, were assessed in the first step of the screening procedure. A sample of 84 boys was randomly selected from a larger pool of 250 kindergarten boys who had an “aggressiveness-hyperactivity-distractibility” score above the 70th percentile on the preschool behavior questionnaire. In the second step, observed task-inappropriate behaviors were compared to mothers' and teachers' ratings of inattention and of aggressiveness (at ages 6 to 7), as predictors of extreme antisocial behavior at age 10. Results indicated that observed task-inappropriate behaviors and teacher ratings of inattention were better predictors of diversity of offending than were mother ratings of aggressiveness. The best predictive combination consisted of extreme scores above the 70th percentile and observations of task-inappropriate behaviors in multiple settings.