This retrospective study assessed the medical necessity of orthognathic surgery for the treatment of dentofacial deformities associated with temporomandibular joint disorders from a perspective of cost effectiveness, myofascial and masticatory function, and quality of life. Questionnaires were mailed to 385 orthognathic surgical patients from one oral and maxillofacial surgery practice. Each questionnaire consisted of three sections: medical costs associated with the patient's orofacial symptoms, symptoms associated with the patient's condition, and the patient's quality of life. One hundred fifty patients responded to the questionnaire. On average, patients spent less money per month on costs associated with their orofacial problem after surgery, and there were fewer visits to the doctor postoperatively. All temporomandibular symptoms were significantly reduced postoperatively, with the exception of facial pain. Quality of life also showed improvement postoperatively. Although orthognathic surgery may be of slightly greater benefit to specific groups of patients based on occlusal relationship and age, all patients in this study showed significant postoperative improvement.