Objective: The term “competitive flow” defines the flow from a partially stenosed native artery that “competes” with the flow from a graft to perfuse the distal tissues. The purpose of our study is to investigate the effects of competitive flow at different degrees of stenosis at common carotid artery, in a rabbit model by measuring both the flow volume and velocity in the venous graft. Methods: This prospective experimental study included 33 rabbits, which were divided into three groups: in Group 1, the common carotid arteries were ligated to form a total occlusion, in Group 2, the common carotid arteries were externally incompletely ligated to achieve 50% stenosis, and in Group 3, common carotid arteries were fully patent. The jugular vein was reversed and anastomosed to proximal and distal common carotid arteries using end to side anastomosis technique. Mean arterial pressure, the total flow and velocity were measured in native carotid arteries prior to surgery and in venous grafts 2 months after surgery using Doppler ultrasonography. Statistical analysis was performed using Chi-square test and Kruskal Wallis analysis of variances. Results: There were no differences in graft mean velocity (Group 1 - 16.8±6.7 cm/sec, Group 2 - 14.1±6.1 cm/sec and Group 3 - 12.1±6.7 cm/sec), and mean flow volume (Group 1 - 33.9±11.5 mL/min, Group 2 - 29.0±8.3 mL/min, and Group 3 - 24.4±12.8 mL/min) between groups after surgery (p>0.05 for both). Conclusion: As it was the case in this rabbit model, the reduction of flow volume or velocity in lesser degrees of stenosis in the carotid artery venous bypass grafts is not significant in a statistical perspective. Although in short-term this effect did not create a difference for graft patencies between the groups, it may be important in long-term