The aim of this study was to compare the provisional diagnosis based on an initial clinical examination with subsequent findings of magnetic resonance imaging in patients with internal derangement of the temporomandibular joint. Clinical examinations were conducted on 242 patients (198 women and 44 men) who had unilateral (51%) or bilateral (49%) temporomandibular joint internal derangement. They were divided into the following categories: (1) disc displacement with reduction; (2) disc displacement without reduction; (3) "stuck" disc; (4) degenerative arthrosis with or without one of the above; and (5) normal temporomandibular joint of the contralateral side. There was no statistically significant difference in the distribution of disorders on a unilateral or bilateral basis or in the prevalence of disorders in right versus left joints. Based on the high occurrence of matching true-negative data, this study showed a highly statistically significant correlation between the magnetic resonance findings and the clinical data for all categories of derangement. Despite this high correlation, the magnetic resonance imaging and clinical diagnoses matched exactly in only 287 of the 484 joints studied. There was only partial agreement in the remaining 197 joints. The best clinical diagnosis in relation to the magnetic resonance findings was observed in the arthrosis category followed by the categories of normal joint, disc displacement with reduction, stuck disc, and disc displacement without reduction, in descending order. This study strongly suggests that degenerative arthrosis is a result of a long-term displaced disc. The clinical examination alone did not correctly indicate all the structural defects; therefore, it is insufficient for determining the status of the joint.