Conduct disorder involves serious behaviour problems such as aggression toward others. It causes heavy burdens for individual children and for their families. It also leads to heavy societal burdens — particularly when the added health care, education, social service and justice system costs are counted. Given these added costs, averting just one case of conduct disorder could save an estimated $4.2 to $7 million over the lifetime — enough to pay for new prevention programs. For more information, see Vol. 1, No. 2 of the Children’s Mental Health Research Quarterly.