Maternal ratings of explosiveness, opposition, and aggression were analyzed in 1609 children 6-16 years of age. Behavior problems were common in autism, ADHD-Combined type, and depression, whereas children with ADHD-Inattentive type, anxiety disorder, and acquired brain injury did not differ from typical controls. More than 40% of children with autism, ADHD-Combined type, and depression met criteria for oppositional-defiant disorder (ODD), and less than 15% did in the other groups. Male gender and low SES increased the risk of behavior problems, but correlations were small between behavior problems and age and IQ. Our findings have implications for new DSM-V diagnostic categories and criteria. The DSM-V needs to clarify whether or not an additional diagnosis of ODD should be made in children with autism who meet ODD criteria. The proposed DSM-V states that ADHD and temper dysregulation disorder with dysphoria not be diagnosed in autism, but does not mention ODD. Our study also suggests that diagnoses of temper dysregulation disorder with dysphoria and prepubertal bipolar disorder may be redundant to a diagnosis of ODD. (Contains 3 tables.)