We carried out a prospective study to assess the short- and long-term outcomes of true eminectomy in 20 consecutive patients with type III or IV anteriorly displaced discs in whom conventional conservative treatment had failed to resolve the symptoms. Maximum opening was measured preoperatively, 3-6 months postoperatively and at one year postoperatively. Each patient filled out a Mandibular Functional Impairment Questionnaire [MFIQ] and Clinical Dysfunctional Index both preoperatively and one year postoperatively. Imaging records included preoperative and one year postoperative orthopantomograph (OPG) and magnetic resonance imaging (MRI). Maximum mouth opening one year postoperatively had increased in 95% of patients (range 5-20 mm, mean 12 mm). There was an improvement in symptoms, using the MFIQ, in 85% of patients. The Clinical Dysfunctional Index was reduced to Type I in most patients. MRI showed increase in rotation and translatory movement of the condylar head. We conclude that true eminectomy may be used to successfully treat type III and type IV anteriorly displaced discs in patients who have failed to respond to conventional conservative treatment.