Background: Lougheed did the first EC/IC bypass surgery using a long-vein graft (1971). In Japan, Iwabuchi did this surgery first (1979), and Eguchi reported his eight cases and stressed the usefulness of a long-vein graft for an EC/IC bypass surgery (1983). For another graft, the radial artery was first used by Ausman (1978), but he reported high frequency of intimal hyperplasia and a poor long-term patency. We have always used, therefore, a saphenous vein for this interpositional graft. We have done this surgery 70 times for 61 cases. Indication: A long-vein graft can be used (1) when a high bypass flow is needed immediately postoperatively and (2) when any donor or recipient vessel, which is located far away from the head or deeply in the head, is selected. Operative and management techniques: (1) Avoiding twisting of the vein graft is mandatory. (2) Postoperative hypertension is most dangerous. (3) Postoperative hypovolemia must also be avoided. Operative results: The mean bypass flow is 109 ml/min ( n=59). The inner diameter of the vein graft decreases with time due to its intimal hyperplasia. But we have confirmed angiographically that the diameter decrease ceases around 6 months postoperatively. The bypass patency rate of our series is 86.7% ( n=60). The complication rate: minor, 21%; major, 7%; fatal, 7%. Conclusion: A long-vein graft is useful for an EC/IC bypass and optimal for an interpositional graft with respect to its patency. We have to understand, however, that it can be a more risky operation than, for example, an STA–MCA anastomosis.