Objective: Use of the radial artery (RA) as a conduit in coronary artery bypass grafting (CABG) has become increasingly popular in recent years. The aim of this prospective randomized study is to determine how the endothelial wall and blood flow of RA are differently affected with the usages of ultrasonic scalpel and conventional electrocautery in addition to effects of hypothermia and storage solutions. Histopathologic study was achieved by electron microscope to evaluate endothelium of the grafts. Methods: Between 2008 and 2009, 182 patients with coronary artery diseases were operated for coronary artery revascularization. The radial arteries were harvested for 40 of these patients and divided into two groups depending on the use of the ultrasonic cautery (UC) (n=20) and the high-frequency electrocautery (EC) (n=20). Patients were divided into two subgroups according to the storage media of the graft. RA was preserved in situ at room temperature (Group 1) and normothermic organ bath (NOB) (Group 2). Harvesting time, use of hemostatic clips, frequency of spasm, in situ free flow, temperature and endothelial damage were compared between the two groups. Statistical analysis was performed using one-way ANOVA, Friedman and unpaired t tests. Results: In all groups, blood flows were significantly decreased as parallel to the local temperatures. Second and third phase flows were similar in group EC1 and UC1 (p>0.05). Free flow was increased in group UC+NOB when comparing with only EC group (60.4±9.83 ml/min and 40.8±7.50 ml/min, p<0.001), whereas the graft preparing time “t2” was shorter in group EC than UC (10.9±2.42 min and 15.2±1.31 min, p<0.01). Nonetheless scoring of the groups in terms of endothelial cell structure and mitochondrial morphological changes did not show any significant difference. Conclusion: If endothelial integrity of the RA can be preserved along with the application of systemic temperature (NOB), regardless of harvesting technique, it provides better flow rates.