The purpose of this study was to attempt to identify those blunt trauma patients in whom expensive diagnostic studies such as computed tomography and diagnostic peritoneal lavage are unnecessary to exclude intra-abdominal injury. The medical records of 1096 blunt trauma patients evaluated at an urban level I trauma center were reviewed. Because of the urgent need to exclude intra-abdominal hemorrhage in patients with hypotension (blood pressure < 90 mm Hg), and the difficulty in obtaining reliable information from abdominal examination in patients with Glasgow Coma Scale scores < 11 or spinal cord injury, 140 patients meeting these criteria were reviewed but excluded from statistical analysis. Six groups of major associated injuries felt to be potential risk factors for the prediction of intra-abdominal injury were analyzed in the 956 remaining patients. Only two of these potential risk factors, namely chest injury (p = 0.0001) and gross hematuria (p = 0.0003) attained statistical significance. All of the 44 significant intra-abdominal injuries occurred in the group of 253 patients that had either an abnormal abdominal examination, one of the statistically significant risk factors, or both, for a sensitivity of 100%. Of the 703 patients with a normal abdominal examination and no risk factors, none had a significant abdominal injury, for a negative predictive value of 100%. This study suggests that patients with either an abnormal abdominal examination or one of the two statistically derived risk factors require adjunctive diagnostic evaluation with diagnostic peritoneal lavage or computed tomography scan to exclude intra-abdominal injury.(ABSTRACT TRUNCATED AT 250 WORDS)