Introduction: This study was designed to test the role of parental supervision in explaining why children with behavior disorders have increased risk of unintentional injury. Method: Children referred to a pediatric behavior disorders clinic and their mothers were unknowingly observed in a "hazard room" environment that housed several items that appeared dangerous but actually were altered to be safe. Results: Mother and child behavior in the hazard room was correlated to parent-, teacher-, and observational-reports of children's externalizing behavior patterns, children's injury history, and mother's parenting styles. Maternal ignoring of children's dangerous behavior in the hazard room was the strongest correlate to children's injury history. Conclusions: Poor parental supervision might serve as a mechanism to explain why children with behavior disorders, and those with oppositional behavior patterns in particular, have increased risk of unintentional injury. © 2006 National Safety Council and Elsevier Ltd.