Introduction: Acute gastrointestinal hemorrhage (GIH) is a medical emergency with a significant morbidity and mortality. Objective of this study was to compare the diagnostic accuracy of CT angiography (CTA) in patients with the various severity of GIH. Material & Methods: We had retrospectively enrolled adult patients (N=262) with GIH who have received CTA during 2 years. Result of CTA was reviewed and the reference standard consisted of endoscopy, conventional angiography, bleeding scan, capsule endoscopy and surgery. Clinical severity was stratified according to the amount of packed RBC transfused during first 2 days. We categorized first quartile as mild, second and third quartiles as moderate, and fourth quartile as severe group. Results: Patients were categorized into mild (n=75, 28.6%), moderate (n=139, 53.1%), and severe (n=48, 18.3%) group. Mean amount of transfused packed RBC was 0, 3 and 9.6 in mild, moderate, and severe group, respectively. Overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of CTA was 73.8%, 94.0%, 97.3%, and 55.3, respectively. Area under the receiver operating characteristics curve of CTA was .780, .841 and .930 in mild, moderate, and severe group, respectively. This was significantly different among groups (p=0.006) (Table 1 and Fig. 1). Conclusion: Diagnostic accuracy of CTA is better with more severe GIH patients.