Primary care physicians who treat attention-deficit/hyperactivity disorder (ADHD) may expect to encounter oppositional defiant disorder (ODD) in about half of patients with ADHD. Up to 20% of patients with ADHD may meet criteria for conduct disorder (CD), and a higher percentage will exhibit aggressiveness or other symptoms of CD without meeting full diagnostic criteria. Primary care physicians self-report more competence in managing ADHD alone than when it is accompanied by comorbid ODD or CD, even though the diagnostic and treatment considerations are similar. The empirical literature on normal and antisocial behavioral development provides insight into understanding how patients with comorbid disruptive behavior may differ from those with uncomplicated ADHD. Primary care physicians who are competent to diagnosis and treat ADHD may develop similar competence in managing patients with ADHD plus oppositional and/or aggressive behavior and, if allied with colleagues who provide specialized psychosocial treatment, may fill an important role in the overall management of complex cases.