This study examined the efficacy of a multimodal intervention with conduct disordered boys in the middle primary years. The intervention consisted of a behavioural classroom program; a small group, social skills program; and a behavioural parenting program Resource implications of this model were also evaluated. A review of the current literature on conduct disorders showed that these children account for less than 5% of the population, but they have a strong impact on families, teachers, peers, schools and the wider community. About 50% of children with severe, early behavioural problems will continue with these problems, not only throughout their adult lives, but into the next generation. Early intervention appears to offer our best hope of altering this trajectory. Interventions with this population have been largely unsuccessful. At the present time the most promising intervention is behavioural parent training programs. Combining these with child focused social skills programs, and behavioural programs in the school setting, increases their efficacy. This study used a single subject experimental design to examine the effects of this program on four boys with behavioural difficulties. Continuous measures were taken with parent, and teacher daily record charts, and classroom observations. Pre, post and followup measures were taken with the Child Behaviour Checklist. The results of the study were mixed. Some subjects, according to some respondents, improved in home and school behaviours. All three subjects, for whom there was followup data, had improved. The classroom, and parenting programs appeared to be associated with positive changes in child behaviour, the small group was associated with more disruptive behaviour at school.