A prospective study was undertaken to compare diagnostic peritoneal lavage with computed tomography in the evaluation of blunt abdominal trauma. Acutely injured patients meeting the advanced trauma life support criteria for lavage were first studied with computed tomography followed by diagnostic peritoneal lavage. Patients underwent exploratory celiotomy for positive results of either study. Computed tomography was read initially by the radiology resident and then by the trauma fellow or senior surgery resident or both. A second interpretation was made by senior radiology staff. Analyses included sensitivity, specificity, false-negative, false-positive, predictive value of positive and negative tests, and accuracy for lavage and each tomography interpretation. Lavage was found to be more accurate than computed tomography in the immediate diagnosis of blunt abdominal trauma and remains the diagnostic test of choice at our institution. Caution is advised in using computed tomography as the primary diagnostic technique until the reliability is demonstrated at any particular institution.