The incidence of internal derangement of the temporomandibular joint has been documented in patients with temporomandibular disorders. However, the detection and diagnosis of a displacement of the temporomandibular joint disc in relation to internal derangement is not always accurate, and it varies according to the method of examination. A prospective clinical investigation of 26 patients (45 temporomandibular joints) with signs and symptoms of temporomandibular joint pain and dysfunction was completed to examine the accuracy of clinical examination, sagittal recording device tracings, arthrography, and magnetic resonance imaging in detecting internal derangement in the temporomandibular joint. A group of 16 asymptomatic control subjects (32 temporomandibular joints) was examined for the presence of internal derangement by the methods under consideration. Incidence of bilateral internal derangement in the temporomandibular joints of the symptomatic patients was also assessed. Findings obtained through clinical examination and sagittal recording device tracings agreed most often with the arthrographic findings of internal derangement. Magnetic resonance imaging often failed to detect the presence of arthrographically detected internal derangement. Internal derangement was identified bilaterally in a significant number of patients, despite the absence of bilateral symptoms. This incidence varied according to the technique used. In the control group, 9% of the temporomandibular joints that had been assessed as normal according to clinical examination and sagittal recording device tracings were found to have internal derangement according to magnetic resonance imaging.