Preoperative and operative evaluation of the arterial reconstructive tract is very important to obtain a high reconstructed graft patency rate after femoro-popliteal bypass. We analyzed the graft patency rate of 40 cases in which the graft flow was measured immediately after completion of arterial reconstruction. The mean graft flow was 122.6ml/min in patients with above-knee (AK) reconstruction and 57.4ml/min in those with below-knee (BK) reconstruction. In cases with AK reconstruction, the three-year cumulative patency rates of grafts with a blood flow of 120ml/min or more (n=12) or less than 120ml/min (n=11) were 100% and 80.8%, respectively (p<0.05). In cases with BK reconstruction, the three-year cumulative patency rates of grafts with a blood flow of 55ml/min or more (n=9) and less than 55ml/min (n=8) were 62.2% and 50.0%, respectively. All early occlusions (n=5) occurred in patients with BK reconstructions. Despite having a blood flow greater than 55ml/min, two cases became occluded in the early stage due to knee joint bending. It is considered that intraoperative measurement of the graft flow is one index to predict graft patency.