Objective To study the effects of glial cell derived neurotrophic factor（GDNF） on regeneration of facial nerve defects by autogenous facial vein conduit. Methods Thirty -six rabbits were used in this study and 10 mm-length facial nerve defects were made on both sides of all animals. The nerve gaps were bridged using autoge-nous posterior facial vein graft of the same side. The animals received injection of either saline（group A, n= 16） or GDNF（group B, n=16） into the veins. Nerve function was evaluated by evoking nerve action potential immediately after operation and 4, 8 and 16 weeks after operation. Regenerated nerve samples were harvested at 4, 8, and 16 weeks after operation and processed for histology and transmitting electron microscopic examination（TEM）. Results Action potential did not exist immediately after operation but it was evoked at 4, 8, and 16 weeks in both groups. At 4 and 8 weeks after operation, the amplitude and width of action potential were significantly higher in group B than group A（P
