PURPOSE: A graft patency is influenced by various factors; the degree of preoperative ischemia, type of procedure, kinds of the conduit and the stati of inflow and outflow vessels. The aim of this study was to evaluate the patency rate according to the distal anastomosis level, kinds of conduit and the impact of runoff score. METHODS: Between August 1998 and August 2003, 141 lower extremity arterial bypass operations were performed. The runoff scores of the outflow arteries were graded according to the system proposed by the Ad Hoc Committee on Reporting Standards, SVS/ISCVS. The graft patency was determined by clinical examination, and ABI measurements, and with a Duplex scan if required, and assessed by a regular follow-up schedule. RESULTS: The primary patency rates according to the level of distal anastomosis at 1, 3 and 5 years were as follows; femoral artery (FA) 94.8, 87.1 and 87.1%, above-knee popliteal artery (AKPA) 83.7, 79.3 and 68.0%, below-knee popliteal artery (BKPA) 85.9, 64.4 and 42.9%, respectively, and the secondary patency rates; FA 95, 87.6 and 87.6%, AKPA 91.6, 68.3 and 38.6%, BKPA 83.8, 69.9 and 46.6%, respectively. The patency rates of below-knee popliteal bypass showed no statistical difference between each conduit, but showed a tendency to increase in the order: PTFE, vein patch and vein graft. No significant difference in the patency rate was shown except between a runoff score of 1 and above 1 at each level. CONCLUSION: The patency rates for the relatively proximal site of the distal anastomosis were superior to those of the distal site. The choice of conduit influenced the patency of infrapopliteal bypass grafts. The patent outflow vessels and the autogenous vein graft at infrapopliteal artery were more favorable for good graft patency. The recommended runoff score system seems to be revision in order to improve the predictability of a graft patency.