Evidence for a diagnostic distinction of oppositional defiant disorder (ODD) and conduct disorder (CD) is reviewed, and alternative conceptualizations and definitions for the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders are considered. Studies suggest that CD and ODD are strongly and developmentally related but clearly different. Factor analyses indicate that distinct covarying groups of ODD and CD symptoms can be identified, but certain symptoms relate to both (particularly mild aggression and lying). Age of onset for ODD is earlier than for most CD symptoms. Nearly all youths with CD have a history of ODD, but not all ODD cases progress to CD. The disorders demonstrate the same forms of parental psychopathology and family adversity but to a greater degree for CD than for ODD. Alternative conceptualizations for the disorders are presented for further study before the introduction of the DSM-IV.