Aims: The aim of this study was to evaluate the diagnostic accuracy in the ass essment of coronary artery bypass grafts using 64-slice computed tomography(CT) technology. Methods and results: CT coronary angiography was performed for 96 b ypasses in 31 patients with suspected coronary artery disease using a Siemens Se nsation 64-slice CT-scanner and compared with invasive coronary angiography(IC A). Patients with an irregular or fast heart rate despite β-blocker administra tion were not excluded from the study. All bypass grafts and 94%of the distal b ypass anastomoses could be visualized by CT, nonevaluable distal arterial anasto moses were either due to clip material or calcification artefacts. Forty-two by pass graft occlusions and three significant stenoses were detected by CT and con firmed by ICA. Two venous grafts were missed and one arterial graft was not eval uable with ICA, but both were clearly depicted by multi-slice CT. One false neg ative and two false positive CT-findings resulted in a sensitivity of 97.8%, a specificity of 89.3%, a positive predictive value of 90%, and a negative pred ictive value of 97.7%. Conclusion: State-of-the-art 64-slice CT coronary angiography demonstrates high diagnostic accuracy in the assessment of arterial and venous bypass graft stenoses. Aims: The aim of this study was to evaluate the diagnostic accuracy in the assessment of coronary artery bypass grafts using 64-slice computed tomography (CT) technology. Methods and results: CT coronary angiography was performed for 96 b -passes in 31 patients with suspected coronary artery disease using a Siemens Sessions 64-slice CT-scanner and compared with invasive coronary angiography (IC A). Patients with an irregular or fast heart rate despite β-blocker administra tion were not excluded from the study. All bypass grafts and 94% of the distal b ypass anastomoses could be visualized by CT, nonevaluable distal arterial anasto moses were either due due to clip material or calcification artefacts. Forty-two by pass graft occlusions and three significant stenoses were detected by CT and con firmed by ICA . Two venous grafts were missed and one arterial graft was not eval uable with ICA, but both were clearly depicted by multi-slice CT. One false neg ative and two false positive CT-findin gs resulted in a sensitivity of 97.8%, a specificity of 89.3%, a positive predictive value of 90%, and a negative pred ictive value of 97.7%. Conclusion: State-of-the-art 64-slice CT coronary angiography demonstrates high diagnostic accuracy in the assessment of arterial and venous bypass graft stenoses.