PURPOSE: We planned to determine the diagnostic capability of focused assessment with sonography for trauma (FAST) in cases of blunt abdominal injury (BAI). METHODS: A retrospective analysis of FAST sheets was performed from April 2002 to December 2004. During the study period, 135 BAI patients were evaluated with FAST at the Emergency Department of Bundang CHA Hospital. Of this group, twenty-eight patients were excluded, leaving 107 patients for analysis. Abdomen CT (computerized tomography) or exploratory laparotomy confirmed the presence of hemoperitoneum. At the secondary survey, patients underwent a three-view FAST examination (LogicQ; General Electric, Waukesha, USA) by an emergency physician, followed within 2 hours by an abdomen CT or exploratory laparotomy. The FAST examination was considered positive if it demonstrated evidence of free intra-abdominal fluid. RESULTS: There were 45 true-positive FAST examination, 57 true-negatives, 1 false-positive, and 4 false negatives (sensitivity 91.8%, specificity 98.3%, positive predictive value 97.8%, negative predictive value 93.4%). The area under the ROC curve was 0.951 for the FAST examination. CONCLUSION: FAST is a highly reliable method for screening patients suspected of having BAI for the presence or absence of hemoperitoneum.