Patients in unstable condition with suspected blunt abdominal trauma require rapid evaluation to assess the need for laparotomy. Ultrasonography is fast and uses portable equipment, and it can be used in the resuscitation area to detect free intraperitoneal fluid as an indication of intraabdominal injury in the patient in unstable condition. To determine the utility of emergency abdominal sonography for evaluating patients with blunt abdominal trauma, a prospective study was designed to compare ultrasonography to diagnostic peritoneal lavage. Emergency sonography was performed prior to diagnostic peritoneal lavage on 54 acutely injured patients in the resuscitation area. Our results reveal that ultrasonography has a sensitivity of 87%, a specificity of 100%, and an overall accuracy of 96% for detecting free intraperitoneal fluid. We conclude that ultrasonography is a reliable method for the emergent evaluation of blunt abdominal trauma and can be used in place of diagnostic peritoneal lavage as the initial indicator of significant intraperitoneal injury requiring surgical intervention.