A study was undertaken to determine the criteria for ordering abdominal computed tomography (CT) in the emergency department (ED) for stable patients who sustained blunt trauma and to identify a patient population at high risk for having intra-abdominal injury (IAI) utilizing physical examination, decrease in hematocrit, and hematuria. Patients in a university ED who had abdominal CT from April 1995 to October 1995 were evaluated prospectively. Before the scan, the examining physician completed an entry form that included physical findings, hematocrit, hematuria, Glasgow Coma Scale score, intoxication, distracting injuries, reasons for obtaining the scan, and planned disposition. Patients were followed until discharge. A total of 196 patients were evaluated. Abdominal tenderness was present in 120 patients. Twenty-two patients had IAI. Eight required surgical intervention, and all 8 had abdominal tenderness. A total of 40 potential trauma admissions were averted by obtaining CT within the ED. The combined abnormal abdomen examination and presence of hematuria had a sensitivity of 64%, specificity of 94%, positive predictive value of 56%, and negative predictive value of 95%. Decrease of > or = 5 in hematocrit was not statistically significant for detection of IAI. CT had no false negatives in this cohort. These results show that early CT scanning of stable patients who have sustained blunt trauma is an effective screen for IAI and may result in fewer total admissions, but has potential for overuse. Patients with abdominal pain and hematuria should be scanned. The benefit of a CT scan for patients without tenderness or with an isolated decrease in hematocrit is questionable.