In this era of conservative management for most infants and children with blunt abdominal trauma, there is a concern that the diagnosis of bowel perforation may be missed or delayed. To determine the sensitivity of CT in the detection of perforated viscus in this population, we reviewed the CT examinations of 547 consecutive children who had had blunt abdominal trauma. Of six patients (1%) with documented bowel perforation, four (67%) had free intraperitoneal air detected preoperatively by CT. The remaining two cases had secondary signs of bowel thickening and unexplained peritoneal fluid. Free intraperitoneal air was not a specific indicator for bowel perforation. Of nine patients in whom CT studies showed pneumoperitoneum, only four (44%) had a ruptured bowel. The remaining five patients had pneumoperitoneum from sources other than bowel perforation including pneumomediastinum, bladder perforation, and previous peritoneal lavage. This experience shows that the CT finding of pneumoperitoneum is useful, although not specific for the detection of bowel perforation in children with blunt abdominal trauma. When free air is not present, secondary signs of bowel wall thickening and unexplained peritoneal fluid suggest a bowel perforation.