Rat sciatic nerves were transected and intubated with a fourteen millimeter lengthsilicone chamber, with two 8 mm windows covered with either a 10 or 60 pm mesh. After six months, the animals were perfused with a glutaraldehyde and paraformaldehyde mixture and the regenerated nerve histology was evaluated at two levels within the chamber (3 mm and midlevel) and 5 mm distal to the chamber. The myelinated nerve fibers were counted and compared for al1 levels and treatments. We found a disorganized endoneurium at midchamber level. Distally, a very low myelinated nerve fibers count was registered. No significant differences were observed between 10 and 60 vm meshes. We conclude that 10 or 60 pm meshes do not control the massive invasion of the chamber by fibroblasts, leading to a highly disorganized regenerated nerve.