Despite important clinical and nosological implications, the comorbidity of oppositional defiant disorder (ODD) and generalized anxiety disorder (GAD) has received little attention. A clinic-based sample of 243 boys (ages 6-10 years), their parents, and teachers participated in an evaluation that involved assessments of behavioral, academic, and family functioning. ODD and GAD symptom groups were defined using various combinations of mother and teacher reports. ODD symptom groups were associated with conduct disorder symptoms, and GAD symptom groups with major depressive disorder symptoms, regardless of rater. Attention deficit/hyperactivity disorder (ADHD) symptoms were associated with ODD and GAD symptom groups; however, covarying ADHD symptoms altered few findings. The ODD + GAD symptom groups were associated with higher rates of co-occurring symptoms and risk factors within (source-specific syndromes) and across (cross-informant comorbidity) informants. (Contains 4 tables.)