We developed a new quantitative rat sciatic nerve model to test whether free fat grafts can reduce postoperative perineural scar formation. Epineurectomies of sciatic nerves were performed to create scar. The force required to distract the nerve a unit distance was measured after surgery to determine the time of maximal scar formation. Nerve stiffness normalized for rat weight was statistically greater at 2 months after the initial dissection (0.097+/-0.009 g/mm/g rat weight; n = 10 limbs) than rat limbs that had not undergone a previous dissection (0.075+/-0.012 g/mm/g rat weight). Perineural scar thickness was thicker at 2 months than the perineural tissue in preoperative controls. Free fat grafts decreased nerve stiffness at 2 months (0.078+/-0.012 g/mm/g rat weight) in comparison to the contralateral surgical control limb without a fat graft (0.094+/-0.014 g/mm/g rat weight). Free fat grafts reduced the strength of postoperative perineural scar in this surgical model; however, they were associated with an unexpected finding of substantial postoperative neuropathy.