In situ saphenous vein bypass, using the new valve incision techniques, has shown great promise in the early clinical trials to date. This procedure allows disruption of the venous valves without removal of the vein from its bed, thus allowing preservation of the vasa vasorum and maintenance of the endothelial integrity of the veins. This has allowed an overall improvement in the patency rates of the lower extremity bypasses, particularly in the bypasses to the infrapopliteal position. Also, and perhaps most important, it has permitted the use of smaller veins, with a minimum diameter of 2 mm. This greatly increases the number of patients who can benefit from such a vein bypass since reversed vein bypasses previously have required veins to have a minimum diameter of 3.5 to 4 mm. Long-term follow-up of in situ bypasses is not yet available. However, if the encouraging preliminary results of these bypasses are substantiated on long-term follow-up, in situ saphenous vein bypass may well become recognized as the procedure of choice for lower extremity bypass.