Despite the satisfactory use of homografts and various prosthetic materials for arterial reconstruction, venous replacement has continued to present a problem. The need for a technique of replacement of obstructed veins and the desirability of having available substitute veins for bypass or reconstruction has led to attempts at replacement with arterial and venous homografts and autografts and with various prosthetic materials. In general, success in reported experimental studies has been only moderate. Crimped knitted Teflon has produced exceptionally good results in arterial replacements, and its physical characteristics produce a greater degree of inherent stability of shape than most other prosthetic materials. For these reasons this material was selected for experimental replacement of segments of the abdominal vena cava and thoracic inferior vena cava in order to assess long-term patency and the degree of maintenance of anatomical integrity. Methods In a series of 15 adult mongrel dogs the inferior vena cava