Objective: To examine risk factors and co-occurring symptoms associated with mother-reported versus teacher-reported anger/irritability symptoms (AIS) of oppositional defiant disorder (ODD) in a clinic-based sample of 1,160 youth aged 6 through 18 years. Method: Participants completed a background history questionnaire (mothers), school functioning questionnaire (mothers, teachers), and "DSM-IV"-referenced symptom checklists (mothers, teachers). Youth meeting AIS criteria for ODD were compared to youth with ODD who met criteria for noncompliant symptoms (NS) but not AIS and to clinic controls. Results: Compared with NS youth, youth with AIS were rated as exhibiting higher levels of anxiety and mood symptoms for both mother- and teacher-defined groups, and higher levels of conduct disorder symptoms for mother-defined younger and older youth. The remaining group differences for developmental, psychosocial, and psychiatric correlates varied as a function of informant and youth's age. Conclusions: Evidence suggests that AIS may constitute a more severe and qualitatively different ODD clinical phenotype, but informant and age of youth appear to be important considerations. (Contains 4 tables.)