In an effort to test the effectiveness of verbal instruction in diminishing aggressive behavior, eight aggressive preschool children were individually instructed by their teacher on the harm that results from aggression, its lack of effects as an interpersonal strategy, and the benefits that result from prosocial alternatives. The eight subjects were chosen as the most aggressive from a group of 19 children at a privately operated day care center (all 19 children were observed during three observational phases, each phase lasting two weeks). Results from a time-lagged design indicated that aggressive behavior decreased and positive behavior increased as a result of the teacher instructions. Data on maintenance of change suggest that possibility of lasting effects. Overall, findings indicate that individually instructing children can be an effective strategy for modifying social interaction. (Author/SB)