Internal derangement of the temporomandibular joint can be defined an abnormal relationships of the meniscus relative to the mandibular condyle, articuar fossa and eminence. This may cause variable mandibular dysfunctions and pain. For diagnosis, arthrography, computed tomography and magnetic resonance imaging are used. In this study, the author reviewed 98 TMJs of 88 patients who were diagnosed as internal derangement througth inferior joint space arthrography at the department of Oral & Maxillofacial Radiology, Dental Hospita, Dankook university through 1986 to 1992. 98 TMJs consisting of 30 disc displcement with reduction, 48 disc displcement without reduction and 20 perforation were studied about clinical and radiological findings. The results were as follows: 1. Internal derangement was found most frequently in the 2nd 3rd decades and the average age of perforation was higher than that of disc displcement with higher than that of disc displcement with reduction. The sexual predilection was 2 times hiher in females. 2. The most frequent chief complaints were TMJ sound in disc displcement with reduction, pain and limitation of mouth opening in disc displcement without reduction and pain in perforation. The duration of the chief complaints was longer in disc displcement with reduction with than in preforation and disc displcement without reduction. 3. Reciprocal click was the most frequently TMJ sound in disc displcement with reduction. History of joint sound in disc displcement without reduction an crepitus in perforation was the most frequent one. 4. The average maximum opening was 45.4㎜ in disc displcement with reduction, 31.4㎜ in disc displcement without reduction and 33.8㎜ in perforation. 5. In the centric occlusion, posterior condylar position was the most frequent in disc displcement with reduction. posterior and concentric condylar position was frequent in disc displcement without reduction, concentric and anterior condylar position in perforation. At 1 inch opening, the same position to articular eminence was most frequently found in disc displcement with reduction, posterior position in disc disp1cement without reduction, posterior and nterior position in perforation was frequently found. 6. Bony changes, especially sclerosis and flattening, was most frequently found in perforation.