Objective: Focused Abdominal Sonography for Trauma (FAST) is widely used for the detection of intraperitoneal free fluids in patients suffering from blunt abdominal trauma (BAT).This study aimed at assessing the diagnostic accuracy of this investigation in a designated trauma centre.Methods: This was a retrospective study of BAT patients over a 6 year period seen in a trauma centre in Hong Kong.FAST findings were compared with laparotomy,abdominal computed tomography or autopsy findings,which served as the gold standard for presence of intrapcritoneal free fluids.The patients who did not have FAST or gold standard confirmatory test performed,had preexisting peritoneal fluid,died at resuscitation or had imcomplete documentation of FAST findings were excluded.The performance of FAST was expressed as sensitivity,specificity,predictive values (PV),likelihood ratios (LR) and accuracy.Results: FAST was performed in 302 patients and 153 of them were included in this analysis.The sensitivity,specificity,positive PV,negative PV,positive LR,negative LR and accuracy for FAST were respectively 50.0 ％,97,3％,87.0％,84.6％,18.8,0.5 and 85.0％.FAST was found to be more sensitive in less severely injured patients and more specific in more severely injured patients.Conclusion: FAST is a reliable investigation iu the initial assessment of BAT patients.The diagnostic values of FAST could be affected by the severity of injury and staff training is needed to further enhance its effective use.