Children with externalizing behavior disorders such as attention-deficit/ hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD) have greatly increased risk of unintentional injury, but it is unclear what mechanisms are responsible for that increased risk. This study followed 22 children participating in a summer camp for children with ADHD. Injury incidents were recorded daily and a set of primary symptoms of behavioral disorders were recorded at 15-min intervals over the course of the 6-week summer camp experience (roughly 300 h of observing each child). We predicted symptoms of ODD and CD would be more strongly related to injury incidence than symptoms of ADHD. Results from univariate Poisson regression models confirmed our prediction. Symptoms of ODD and CD - violations and intentional aggression in particular - were related to injury incidence but symptoms of ADHD were not. This finding is consistent with a growing body of evidence that oppositional, noncompliant, and aggressive behavior patterns might be primarily responsible for increased risk for injury among children with externalizing behavior disorders. © Springer Science+Business Media, LLC 2007.