[en] This paper reported the usefulness of MRI diagnosis in the estimation of the articular disk, especially in the internal derangement of the temporomandibular joint (TMJ). MRI was carried out with 1.5 Tesla (Signa GE Co.). Spin echo sequence was used in this study. Parasagittal sections in open and close mouth positions were obtained in each case. Images were discussed with a repetition time (TR) and an echo time (TE) of 400 ms/10 ms, 1000 ms/20 ms, 2000 ms/30 ms, 2000 ms/80 ms. MRI examination of 87 patients (aged 12-74 years, 15 males and 72 females, 169 TMJs) was performed from August, 1991 to July, 1992. The conclusions obtained were as follows: 1) The condition with a TR 1000 ms, a TE of 20 ms, was the best for detecting the articular disk and its surrounding soft tissues. 2) The detection of the articular disk was achieved in 96.2% of cases. 3) Location of the articular disk on MRI corresponded with clinical symptoms in 77.2% of cases. MRI was one of the most useful methods for the estimation of the articular disk. (author)