The reliability of ultrasonographic detection (US) of hemoperitoneum in blunt abdominal trauma was evaluated in a prospective study of 72 patients. Independent of the examiner, sensitivity, specificity, and accuracy were, respectively, 86.7%, 100%, and 97.2%. Laparotomy was indicated in 76.9% of US hemoperitoneum-positive cases. No negative laparotomies were performed in this study group. If hemoperitoneum is revealed in US and vital signs are unstable, we think laparotomy is indicated. We believe that US in an emergency center is a quick, safe screening method in the evaluation of blunt abdominal trauma. US might take over a great part of the role of diagnostic peritoneal lavage.