Spiral CT (SCT) differs from conventional CT in that the entire heart can be rapidly imaged in the axial plane following the peripheral infusion of small quantities of contrast material. As contrast material travels through coronary artery bypass graft segments, good image detail is achieved, allowing visualization of entire coronary artery graft segments during a single injection. The patency of 43 coronary artery bypass grafts in 14 patients on contrast enhanced SCT, with timing tailored to patient-specific transit times, was compared with that obtained by selective graft angiography. With use of 5 or 8 mm/s table feed and 24 s volumetric acquisitions, SCT established graft patency with 85.7% sensitivity and 100% specificity compared to angiographic examination (96.4% sensitivity and 100% specificity). The mean time between angiography and SCT was 2.1 days, with 86% of SCT studies done within 24 h after angiography. The utilization of dynamic scanning to establish the patient-specific time delay prior to initiation of SCT proved crucial in improving the quality and reliability of SCT bypass graft patency assessment. The paired McNemar test indicates no significant difference between angiography and SCT in establishing patency rates.