Coronary artery bypass surgery with use of either venous or internal mammary artery (IMA) coronary artery bypass grafts has become an established treatment for symptomatic multi-vessel coronary artery disease. One of the most important variables that determine the successful clinical outcome of coronary artery bypass graft placement is the short- and long-term patency rate of the grafts. So far, conventional coronary angiography has been considered the standard of reference for evaluation of the patency and luminal stenosis of coronary artery bypass grafts. However, the main drawbacks of conventional coronary angiography for this purpose include invasiveness, patient discomfort, and risk of complications. A less invasive imaging modality is desirable for evaluation of patients suspected of having graft stenosis or occlusion. The use of multi–detector row CT is gaining increasing acceptance for noninvasive cardiac imaging. Recent years with the new emerging machines have demonstrated successful application of multi–detector row CT angiography for the less invasive assessment of coronary artery disease and the evaluation of coronary grafts. The aim of this study is to evaluate multi-detector row CT angiography as a less invasive technique in the assessment of the coronary arteries bypass graft (CABG). Those are high risk patients and they may not need to undergo much more invasive techniques (e.g. conventional angiography) to assess the patency of their grafts. This study included 62 patients with prior CABG surgery, 24 of them underwent conventional angiography as a gold standard for evaluation of the coronary artery bypass grafts. The indications of angiography were unstable angina in 41 cases (66%). The mean age of the included patients was 58 with an age range between 39 and 73 years. Male patients were 55 (88.7%) while females were 7 (11.3%). A total of 169 coronary artery bypass grafts were included in this study. Out of these 5 were non-evaluable (3%) due to calcification or nearby surgical clips and were excluded from the study. Within the evaluable grafts 72 (43.9%) were arterial and 92 (56.1%) were venous. Out of the arterial grafts, 57 (79%) were find patent, 7 (9.7%) were significantly narrowed and 8 (10.3%) were completely occluded. As for the venous grafts they were 92 grafts, 43 (46.7%) of them were patent, 14 (15.3%) were significantly narrowed and 35 (38%) were completely occluded. Twenty one patients underwent both conventional and MSCT coronary angiography. The patients who did not perform the conventional angiography were mostly due to the decision made by the referring physicians as there is increased confidence in the results of MSCT angiography, so those patients were referred for either conservative medical treatment or for a re-do. 47 grafts were evaluated by conventional angiography, 15 of them were LIMA insitu arterial grafts, 4 free radial artery grafts and 28 venous grafts. Conventional angiography was considered the gold standard technique and using it 12 of the LIMA grafts were seen patent, 1 narrowed and one occluded. One of the LIMA grafts was considered non-evaluable by MSCT angiography because of extensive beam hardening artifacts caused by the adjacent metallic clips. CT angiography compared to the conventional angiography as a gold standard technique gave us a sensitivity of 100%, a specificity of about 96% and an accuracy of about 93.6% in the assessment of any type of coronary artery grafts. The latest multi-slice CT scanners show a potential to become a first-line tool for the noninvasive evaluation of patients with suspected graft dysfunction. Conventional angiography may be spared for patients who needs an intervention e.g. angioplasty or stent placement within a graft or within a native coronary artery.