The Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV; American Psychiatric Association, 1994) specifies a developmental relationship between oppositional defiant disorder (ODD) and conduct disorder (CD). Evidence for this link is mixed, however, and recent studies suggest that different symptom dimensions in ODD may have different outcomes. The authors examined links between ODD, CD, and their young adult outcomes in the Great Smoky Mountains Study (E. J. Costello et al., 1996), a longitudinal data set with over 8,000 observations of 1,420 individuals (56% male) covering ages 9-21 years. ODD was a significant predictor of later CD in boys but not in girls after control for comorbid CD and subthreshold CD symptomatology. Transitions between ODD and CD were less common than anticipated, however, particularly during adolescence. The authors examined characteristics and outcomes of children with pure ODD, pure CD, and combined CD/ODD. Alongside many similarities in childhood and adolescent correlates, key differences were also identified: CD largely predicted behavioral outcomes, whereas ODD showed stronger prediction to emotional disorders in early adult life. Factor analysis identified irritable and headstrong dimensions in ODD symptoms that showed differential prediction to later behavioral and emotional disorders. Overall, the results underscore the utility of retaining separate ODD and CD diagnoses in DSM-V.