PURPOSE: We evaluated the diagnostic accuracy of a 64-slice multi-detector CT (MDCT) coronary angiography against a conventional coronary angiography (CCA) for the detection of significant stenosis (> or =50% lumen diameter narrowing). MATERIALS AND METHODS: Sixty-four patients underwent a MDCT and a subsequent CCA to evaluate the presence of atypical chest pain or suspected coronary artery disease (CAD). A MDCT angiography was performed using a 64-slice MDCT-scanner (Sensation 64, slice collimation 32x0.6 mm). The coronary artery segments were classified according to a 15-segment model. The sensitivity, specificity, and diagnostic accuracy of the 64-slice MDCT for the detection or exclusion of significant CAD were calculated on a per-segment and per-patient basis. RESULTS: Fifty-nine of the 64 (92%) coronary CT angiograms were of diagnostic image quality with 93.5% (809 of 865) of the coronary segments assessable by CT angiography. One-hundred two (12.6%) segments showed significant stenosis by CCA. Stenosis of 50% or greater was detected by sensitivity, specificity, accuracy, positive predictive valve, and negative predictive value on a per segment basis (89%, 99%, 97%, 90%, and 98%, respectively) and a per-patient basis (96%, 69%, 90%, 92%, and 82%, respectively). CONCLUSION: The 64-slice MDCT coronary angiography demonstrated a high diagnostic accuracy for both the per-segment and per-patient analyses for this symptomatic patient group.