Regeneration of both median nerves was studied in the rat in three different experimental models of centrocentral anastomosis through an interposed segment of pre-degenerated tibial nerve after denervation by spinal root transection. Different patterns of regeneration were observed in the anastomoses. These patterns suggest a bio-electrical polarity related to neuronal function. The present experimental model appears to offer a new opportunity to study neuronal regeneration under the influence of defined bioelectrical conditions.