In the rat, a characteristic response to motor denervation is an increased flow of inorganic phosphate across the muscle cell membranes. This reaction is specific for the neurogenic atrophy and is fully reversible on reinnervation. In the present study, the muscle cell permeability to inorganic phosphate has been used as a criterion in assessing the efficiency of four different techinques. Microsurgery was carried out on peroneal nerve using a Zeiss OMP I operating room microscope. The technique were: I. Bringing together the two nerve segments with two epineural stitches (Ethilon 11/0 thread). II. Tight suture with eight epineural stitches (Ethilon 11/0 thread). III. As in II but with SSC 11/0 thread. IV. As in III but combined with postoperative corticotherapy. 32P radiophosphate incorporation was measured in the extensor digitorum longus and in the tibialis anterior. The best results were obtained with the first and simpler procedure. However, in some respects, equivalent results were observed with the fourth procedure associating a tight suture with postoperative corticotherapy. It follows that in the rat, it is indicated either to minimize the surgical trauma or to counteract the fibrosis attending the surgical trauma.