Aim: To analyze the one-year-patency of infrainguinal arterial reconstructions in relation to venous graft diameter and length and the run-off segment, when arteries above the proximal anastomosis of the reconstruction are not diseased.Material and Methods: We compared retrospectively for two-year period the diameter, the length of the used vein and the run-off segment in 107 consecutively constructed infrainguinal autovenous bypasses -54 patent (not less than 1 year) and 53 failed bypasses Diameter of the vein was measured at the narrowest part of the vein (in all cases this was the area of the distal anastomosis). Аll bypassеs are made with translocated nonreversed vein and the length of the vein was measured after the completion of reconstruction. Volume and pressure of blood flow were measured below the distal anastomosis by the means of ultrasound transit-time flowmetry. For the assessment of run-off segment Fourier analyses of flow and pressure were used and alteration of the amplitudes after intragraft infusion of Prostaglandines was calculated.Results: We compared the alteration in amplitudes in failed and patent for at least 1 year bypasses and estimated that ratio below 2 before and after medicamentous vasodilatation, sets the reconstruction in the group of threatened, as well as graft diameter below 3.5 mm and length over 40 cm.Conclusion: Hemodynamic assessment of blood flow below distal anastomosis defines the necessary vein lenght, that is why run-off segment has the most important significance for the patency of the infrainguinal autovenous reconstructions. Shorter grafts with diameter over 3.5 mm do not guarantee longer patency if distal anastomosis is constructed above diseased run-off segment.