The graft patency of bypass surgery to or distal to the popliteal artery for 29 lower extremities with thromboangiitis obliterans (TAO) and for 67 lower extremities with arteriosclerosis obliterans (ASO) and six factors influencing graft patency were studied and a new method of scoring distal runoff determined from angiographic findings was employed.Early graft occlusion (EGO, < one month) was found only in lower extremities with distal runoff of 5 or less and more frequently in patients with TAO than in those with ASO, although distal runoff in TAO patients (n=29) was significantly less than that in ASO.Among TAO patients with distal runoff of 5 or less, EGO (n = 7) was found only in those without concomitant lumbar sympathectomy (CLS), but the difference in distal runoff between patients with EGO and those without it was not significant.From these results, it was concluded that: (1) EGO in patients with TAO is probably due to poor distal runoff with high constrictivity and (2) CLS for such patients could improve EGO, which, in turn, would result in a better cumulative patency rate.