The previously stated advantages of the valve incision method of in situ saphenous vein arterial bypass have now been confirmed by others. However, this method has been limited by its time-consuming technical demands. Considerable experience with this bypass in conjunction with retrograde serial valve disruption with instruments of similar design principle (by Hall and Cartier) has been accumulated in Europe. However, the combination of the trauma of blunt valvular fracture and the sensitivity of endothelium to frictional shear has precluded use of these instruments in veins less than 4 mm in size, and the results have not been significantly better than those obtained with reversed vein bypass. An instrument (valve cutter) that achieves serial valve incision safely and consistently without mandatory exposure of each valve site has now been developed. Of the last 166 consecutive bypasses, the saphenous vein was suitable for use of this instrument in 116 instances (70%). The patency of these bypasses as determined by life-table analysis has shown no significant difference when compared with bypasses performed under similar conditions in which the cutter was not used. On the basis of this investigative and clinical experience, the majority of in situ saphenous vein arterial bypasses can be safely facilitated and simplified by use of this instrument.