The aim of the study was to carry out a systematic review determining the accuracy of CT angiography in the diagnosis of acute gastrointestinal bleeding. A search of published work in Medline and manual searching of reference lists of articles was conducted. Studies were included if they compared CT angiography to a reference standard of upper gastrointestinal endoscopy, colonoscopy, angiography or surgery in the diagnosis of acute gastrointestinal bleeding. Eight published studies evaluating 129 patients were included. Data were used to form 2 x 2 tables. Computed tomography angiography showed pooled sensitivity of 86% (95% confidence interval 78-92%) and specificity of 95% (95% confidence interval 76-100%), without showing significant heterogeneity (chi(2) = 3.5, P = 0.6) and (chi(2) = 5.4, P = 0.6), respectively. Summary receiver operating characteristic analysis showed an area under the curve of 0.93. Computed tomography angiography is accurate in the diagnosis of acute gastrointestinal bleeding and can show the precise location and aetiology of bleeding, thereby directing further management. Strong recommendations for use of CT cannot be made from this review because of the methodological limitations and further large prospective studies are needed to define the role of CT in acute gastrointestinal bleeding.