Background. Arterial composite graft has been demonstrated to have better long-term patency rate than that of saphenous veing graft in off-pump coronary artery bypass surgery (OPCAB). However, arterial graft in elderly patient is often diseased. We sought to compare early and midterm outcomes of the two composite grafts. Methods. We conducted a randomized trial comparing radial artery (RA) with saphenous vein graft (SVG) as a composite graft based on the in situ left internal mammary artery in 60 elderly (>70 years old) patients who were planned to undergo OPCAB, and who were considered suitable candidates for using both conduits. Quality of each composite conduit was evaluated using vascular ultrasonography, optical coherence tomography (OCT), and histologic examination. Clinical outcomes and 1-year postoperative coronary CT results were compared. Results. No difference in immediate postoperative morbidity and mortality was observed between the groups. Vascular ultrasonographic imaging for conduit was reproducible and showed a strong correlation with OCT, and histopathology. Early postoperative coronary CT revealed a SVG patency rate of 98.9%, which was not different from that of RA composite grafts (98.8%). One-year postoperative coronary CT showed an overall patency rate of 96.9%. The patency rate of SVG at 1 year was 94.1%, which was similar to that of RA grafts (97.9%). Major adverse cardiac events-free survival at 1 year was zero. No difference was observed in overall survival rate between the groups. Conclusions. Vascular ultrasonography provides an accurate, real-time reproducible means for assessing the quality of RA conduit. Our early and midterm clnical outcomes revealed that the SVG may be used in elderly patients as an alternative composite graft to the RA graft.