Families of 159, 4- to 8-year-old children with oppositional defiant disorder (ODD) were randomly assigned to parent training (PT); parent plus teacher training (PT + TT); child training (CT); child plus teacher training (CT + TT); parent, child, plus teacher training (PT + CT + TT); or a waiting list control. Reports and independent observations were collected at home and school. Following the 6-month intervention, all treatments resulted in significantly fewer conduct problems with mothers, teachers, and peers compared to controls. Children's negative behavior with fathers was lower in the 3 PT conditions than in control. Children showed more prosocial skills with peers in the CT conditions than in control. All PT conditions resulted in less negative and more positive parenting for mothers and less negative parenting for fathers than in control. Mothers and teachers were also less negative than controls when children received CT. Adding TT to PT or CT improved treatment outcome in terms of teacher behavior management in the classroom and in reports of behavior problems.