The diagnostic arthroscopy was performed on 47 temporomandibular joints from 40 patients having anterior disc displacement without reduction with restricted mouth opening or painful anterior disc displacement with reduction. All patients were outpatients and subjected to arthroscopic examination under local anesthesia. Previous to arthroscopy, routine clinical and radiographic examination, and magnetic resonance imaging were carried out for all joints. Adhesion was better observed by arthroscopic examination, perforation was suggested by magnetic resonance imaging as well as arthroscopic examination, and bone change was better observed by magnetic resonance imaging. However diagnostic arthroscopy should be considered as an invasive examination, it is practical to the clinician and patient as complementary to decide the indication of arthroscopic surgery, open surgery (diskectomy) or maintenance of conservative treatment.