PURPOSE: To evaluate the condylar movement at maximal mouth opening on MRI in patients with internal derangement. MATERIALS AND METHODS: MR images and transcranial views for 102 TMJs in 51 patients were taken in closed and maximal opening positions, and the amount of condylar movement was analyzed quantitatively and qualitatively. RESULTS: For MR images, the mean condylar movements were 9.4 mm horizontally, 4.6 mm vertically and 10.9 mm totally, while those for transcranial views were 12.5 mm, 4.6 mm, and 13.7 mm respectively. The condyle moved forward beyond the summit of the articular eminence in 41 TMJs (40.2%) for MR images and 56 TMJs (54.9%) for transcranial views. CONCLUSION: The horizontal and total condylar movements were smaller in MR images than in transcranial views.