department for an unintentional injury had an increased risk of injury for 90 days after the event. Risk of injury was highest 4 -- 10 days after the event, and risk was higher among older children. *Data provided by author. Commentary 2 Professor, School of Nursing McMaster University Hamilton, Ontario, Canada Unintentional injury is a leading cause of death and disability in children. 1 The study by Johnston et al is based on the premise that prevention of childhood injuries might be more effective if interventions were targeted at children known to be at high risk. In fact, the authors cite various studies that have shown that the risk of childhood injuries is associated with sociodemographic traits, family characteristics, behavioural problems, temperament, stressful life events, and previous injury experience. In their study, Johnston et al found that among urban children enrolled in Medicaid, an injury treated in the ED was a significant risk marker for subsequent sibling injury during the 90 days after the initial event. In particular, the risk peaked in the second week, indicating that families may experience transient high risk periods rather than being permanently at risk. The study has various strengths and limitations. The investigators studied a large sample of children and tried to avoid "double counting" an injury by excluding non-ED clinic settings where the children might have attended for follow up. The reliance on Medicaid claims posed some problems: siblings were linked even if they did not reside in the same household; accuracy of