The clinical significance of hematuria in children who sustain blunt abdominal trauma continues to be debated, as do the criteria for diagnostic imaging in this population. Previous reports have discussed the usefulness of certain clinical predictors of renal injury, such as the amount of hematuria present, the presence of shock or of head injury, and the presence or absence of symptoms or findings on physical examination. To assess the value of such predictors of renal injury in children with posttraumatic hematuria, we reviewed and analyzed the medical records and abdominal CT examinations of 256 children with blunt abdominal trauma. One hundred six children (41%) had hematuria. Thirty-five patients (14%) had renal injury that could be diagnosed by using CT. Nine of these had clinically significant injuries according to our criteria. We found a direct relationship between the amount of hematuria and the severity of renal injury. Hypotension at presentation occurred in 38 patients and was an insensitive predictor of renal injury. The combination of hypotension and hematuria was no more sensitive than hematuria alone in predicting renal injury. Sixty patients had concomitant craniofacial injuries. This subgroup had the same prevalence of hematuria and renal injury as the group that did not have head injuries. There were no clinically occult renal injuries in the study population. Furthermore, we found that no normotensive child with fewer than 50 RBCs per high-power field had a significant renal injury, and conversely, all children with significant renal injuries had either large amounts of hematuria or shock.