Purpose: The aim of this study was to investigate the effect of local administration of Nerve Growth Factor-7S (NGF-7S) on the axonal regrowth of mixed peripheral nerves through nerve or inside-out vein grafts. Materials and methods: One hundred and twenty male Wistar rats were randomised in four groups of thirty animals each. A defect, 12 mm long in the right sciatic nerve, was inflicted and repaired either with a nerve autograft (group A and B) or an inside-out vein graft (group C and D). NGF-7S (group A and C) or normal saline (group B and D, control groups) was locally administered daily during the first 3 weeks. For this purpose, a subcutaneously implanted reservoir connected to a silicone tube was used. Electrophysiologic and histologic - morphometric studies were carried out at 4, 6, 8, 10 and 12 weeks post-operatively (subgroups a, b, c, d and e, respectively, n=6 each). Results: Histologic appearance of cross sections was better in the NGF groups, with better axonal orientation and distribution. Analysis of variance and linear regression analysis showed that NGF consistently provided a significant increase in the average number, the myelin thickness, and the diameter of myelinated axons throughout the course of time (group A vs. B and group C vs. D). Most importantly, electrophysiologic findings verified the beneficial effect of NGF on motoneuronal regeneration, since the recovery of the compound muscle action potential was faster in the NGF treated-groups and reached the normal value at 8 (group A) and at 6 (group C) weeks. Conclusion: According to these findings, there is a strong evidence of the beneficial effect of NGF-7S on peripheral nerve regeneration through nerve and inside-out vein grafts.