Temporomandibular joint (TMJ) sound recordings could be analyzed to assess the state of TMJ internal derangements.The aim of the study was to assess the value of sound analysis in the diagnosis of the type of the TMJ internal derangements.After clinical and radiologic examinations, phonographic sound recordings on mandibular excursions were obtained in 52 patients with TMJ internal derangements and 12 control individuals. Sound correlations were made on the basis of opening-closing, protrusive-retrusive, and lateral excursions of the mandible.Clicking was a consistent finding of anterior disc displacement with reduction, whereas crepitation was found in varying degrees in anterior disc displacement and osteodegenerative arthritis. Silent TMJs were the feature of normal TMJs, except for the situations of acute lock. Although in 29 TMJs opening click was followed by a closing click (reciprocal clicking), 46 TMJs with opening click also had clicking on protrusion. On the other hand, 19 TMJs with opening click also had clicking on ipsilateral motion, and 40 TMJs with opening click had clicking on contralateral motion of the mandible. The sound patterns were found to be similar in opening-protrusive clicks and opening-contralateral clicks. The lack of protrusive clicking in the presence of opening click was considered an indication of late disc reduction on opening. Crepitation was observed in advanced cases of TMJ internal derangements.Within the limitations of this study, the results suggest that TMJ sound analysis on mandibular excursions was indicative for diagnosis and establishment of severity of TMJ internal derangements. Clicking and crepitation may be looked on as signs of abnormal joint disorder, clicking indicating anterior disc displacement with reduction, and crepitation, indicating progression from anterior disc displacement without reduction to osteodegenerative arthritis.