A report of ten-year follow-up examinations of a patient who had a hemimandibulectomy with disarticulation because of fibrous dysplasia and immediate permanent reconstruction of the mandible with a Vitallium custom-cast prosthesis is presented. Careful preoperative planning, operative technique, and postoperative follow-up examinations are essential for successful maintenance of the prosthesis. Autogenic bone grafts are, in general, superior to alloplasts in permanent reconstruction of defects in mandibular continuity after resection. However, there are indications for alloplastic reconstruction when the condyle is disarticulated with the resection.