In recent years, nerve autografting has become widely accepted as an ideal treatment method for peripheral nerve injuries, when there is a large defect or severed nerve ends cannot be approximated without tension at the suture line. However, since the sources of autogenous nerve grafts are limited, for the cases where a large number of autogenous nerve grafts are required as in the surgical treatment of brachial plexus injury, additional grafts are taken from the aleady-injured nerves whose recovery is considered impossible or whose function is not crucial. For the nerve grafts to function properly, they must have a sufficient number of endoneural tubes of appropriate size to provide a conduit for the regenerating axons. It is known that once a peripheral nerve is severed, the distal segment undergoes Wallerian degeneration and the size of the lumens of endoneural tubes deceases. This reduction occurs rapidly during the first 3-4 months and there is little further change thereafter. These findings suggest that the efficiency of an old degenerated nerve graft would be less than that of a fresh nerve graft. Since most nerve graftings are performed microsurgically, they take a lot of time and effort. Therefore, if the fuction of an old degenerated nerve graft is much inferior to that of a fresh nerve graft, it will be better not to use an old degenerated nerve as a graft. In order to compare the ability of old degenarated nerve autografts as a passage for the regenerating axons with that of fresh nerve autografts, an experimental study was conducted on two different groups of Sprague Dawley rats. In one group, the right sciatic nerves were severed and then repaired with the nerve grafts taken from the distal segment of the left sciatic nerves which had been severed 15 weeks before. In the other group, severed right sciatic nerves were repaired with the nerve grafts taken from the left intact sciatic nerves. Eight weeks later, myelinated axons were counted for the both groups at the three different locations of the grafted right sciatic nerves(at the distal end of the proximal segment, at the middle of the nerve graft and at the proximal end of the distal segment). The results showed that with statistical sognificance([t]<0.05),the ability of an old degenerated nerve autograft as a passage for the regenerating axons was less than that of a fresh nerve autograft, but the difference was not large enough to discourage the use of an old degenerated nerve as a graft.