The initial physical examination is frequently unreliable in identifying patients with blunt trauma at high risk for having serious intra-abdominal injury. Intra-abdominal injury may be associated with specific injuries or risk factors, but the usefulness of such objective clinical criteria in predicting intra-abdominal injury has not previously been determined. The presence or absence of each of 11 clinical indicators and their association with serious intra-abdominal injury were analyzed in 3223 patients with blunt trauma. Linear and logistic regressions were used to determine which factors were significant predictors of an increased probability of intra-abdominal injury. Arterial base deficit less than -3 mEq/L, major chest injury, hypotension, and pelvic fractures were found to significantly increase the chance of intra-abdominal injury. Early diagnostic evaluation of the abdomen using diagnostic peritoneal lavage or computed tomography should be strongly considered in patients with blunt trauma who present with these associated factors.