Purpose: To investigate the accuracy of CT coronary angiography (CTCA) in the assessment of coronary artery disease. Method and Materials: Sixteen patients (42-79 yrs) undergoing CTCA and invasive coronary angiography (ICA) were included in this study. All patients were pre-treated with oral propranolol, 40 -80mg, 1 hr before the CTCA to achieve an acceptable heart rate of less than 65 bpm. CTCA were obtained with a 12 X 0.75 mm, 420 ms rotation, multi-slice CT scanner (SOMATOM Sensation, Siemens Medical System) using non-ionic contrast (80ml, 4 ml/sec). All CT data were evaluated by two independent radiologist using transverse scans and multiplanar reformations. The segmental plaque load was assessed following the classifications of the American Heart Association, which subdivide the coronary artery territory into 15 segments and distinguish between 6 different degrees of atherosclerosis: irregular wall outline with <25% stenosis; slight stenosis (25-50%); moderate stenosis (51-74%); high grade stenosis (75-89 %); subtotal stenosis (90-99%); total occlusion. All finding were compared to the results obtained from QCA performed by cardiologist without knowledge of the CTCA results.Results: Proximal segments were visualized all patients. Proximal segments agreement between CTCA and ICA was 92.2% (59/64 segments). Mid-vessel agreement was 90% (58/64 segments) for all patients. Distal vessel (diameter > 1.5 mm) and side branch agreement was 89.5% (43/48 segments), 84.3% (54/64 segments) respectively. Total sensitivity of CTCA in the detection of hemodynamically relevant stenoses (>75%) amounted to 76.5%, specificity to 96.1%. For proximal segments a sensitivity of 83% and a specificity of 100% were obtained. For mid-vessel segments values were 80%, 92.5% respectively, for distal segments 66.6%, 100% respectively, and for side branches 67%, 95% respectively. Agreement between CTCA and ICA was reduced mainly in distal segments and side branches, and the stenoses were overestimated in segments with calcified plaque. Conclusions: CTCA with improved spatial resolution and pre-treated with oral beta-blocker permits detection of coronary artery stenosis with high accuracy.