Authors studied on the T.M.J. dislocation of 5 cases who were visit Dental College Infirmary, S.N.U. The results were obtained as follows. 1) The main symptoms are pain, cracking sound, discomfort of temporomandibular joint region and swelling. 2) All cases except only one case, no specific etiological factors were detected in related to habitual custom and hoby. 3) The patients are all female aged from 19 to 24 years old.