In North America, the role of emergent abdominal sonography [ultrasonography (US)] after blunt trauma requires further definition. The purpose of this prospective study was to compare US to the gold standards, diagnostic peritoneal lavage (DPL), and computed tomography (CT), in a population of adults after blunt trauma. In 206 adults who required either CT or DPL to assess possible abdominal injury, US was performed, before DPL or CT, and was aimed at the detection of intraperitoneal fluid. The mean Injury Severity Score and Glasgow Coma Scale score were 24.0 and 11.9, respectively. One hundred thirty-seven patients (67%) had CT and 69 (33%) had DPL. The positive and negative predictive values of US for intraperitoneal fluid were 90% and 97%, respectively. The sensitivity, specificity, and accuracy of US for free fluid were 81%, 98%, and 96%, respectively. Of the six false-negative USs, only one required surgery. The US examinations required 2.6 +/- 1.4 min. Emergent abdominal sonography is an accurate, rapid test for the presence of intraperitoneal fluid in adult blunt trauma victims and in these patients may prove valuable as a screening test for abdominal injury.