We studied 131 temporomandibular joints (TMJs) in 73 patients (56 women, 17 men) with internal derangement using magnetic resonance imaging (MRI) in addition to clinical examinations. The type of TMJ sounds correlated significantly with the degree of disc displacement. Rounded and folded disc deformities caused crepitus, which was a sign of the advanced stage of anterior disc displacement without reduction. Tenderness on palpation of the lateral pterygoid muscle was found in anterior disc displacements with or without reduction. The more deformed the TMJ disc that was shown on MRI the more substantial the clinical signs and symptoms. As the MRI results correlated well with the clinical findings we concluded that expensive diagnostic methods such as MRI should be used for surgical planning and in difficult cases to diagnose pathological conditions of the TMJ. © 2002 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Science Ltd. All rights reserved.