The relative validity of the reports of parents, teachers, and children, and combinations of these informants was assessed using measures of concurrent impairment associated with disruptive behavior disorders as criterion variables in a clinic-referred sample of 177 boys ages 7-12 years. For oppositional defiant disorder (ODD) and conduct disorder (CD), the reports from teachers, alone and in combination with parents and children, showed the strongest relations to impairment criteria. The reports of parents and children, alone and in combination, were relatively less valid. For attention-deficit hyperactivity disorder, there were no significant correlations between the reports of any single informant or combination of informants and the impairment criteria. This study provides preliminary support for the validity of multi-informant diagnostic assessment of ODD and CD in children, especially when the teacher is one of the informants.