A case has been reported to illustrate the apparent transition of a neurofibroma into a neurofibrosarcoma. Biopsy of the inferior alveolar nerve, proximal to the lesion, was used to determine the extent of tumor extension. En block excision of the tumor was performed. The patient has been without evidence of recurrence for approximatley 3 1/2 years. Bone graft reconstruction has been completed and full function has been restored to the mandible.