Diagnostic peritoneal lavage (DPL) and computed tomography (CT) are the primary diagnostic modalities in the evaluation of patients with suspected blunt abdominal trauma (BAT). Diagnostic peritoneal lavage is fast and accurate but associated with complications. Computed tomography is also accurate, yet requires that patients be stable and transportable. A prospective study was designed to determine the utility of emergency ultrasound (US) studies in the initial assessment of BAT. Two hundred acutely injured patients with suspected BAT were evaluated with US. Patients were eligible for the study if they met trauma criteria and had suspected BAT. Subsequently, without knowledge of the US results, DPL or CT was performed. Ultrasound showed a sensitivity of 83%, a specificity of 100%, and an accuracy of 97% in detecting intra-abdominal injuries. Six injuries were missed but only one was felt to be significant. If US had been used in all 200 patients, 199 would have had appropriate care. We conclude US is reliable in the detection of free intraperitoneal fluid and may be used in place of DPL or CT.