In cases of a serious post-thrombotic syndrome in which conservative treatment has failed, the possibility of a venous femoralis bypass should be considered. Prerequisites for this procedure are an adaequate v. saphena magna and an open or recanalised v. poplitea at the confluens of the vv. tib. post. et vv. fib. This method was first described by May and Husni; we have modified it by replacing the original end-to-side anastomosis with a more effective end-to-end anastomosis and have added a subfascial av-fistula. Both procedures lower the ambulatory venous pressure. This operation has been performed 23 times; the paper presents the late results from 18 patients, 5 of whom underwent the operation over 8 years ago.