In the evaluation of orbital lesions in Basedow disease, the size of the extraocular muscles (diameter of the muscle belly, muscle length and overall diameter of all muscles) and the anterior protuberance of the eyeball from the orbit are measured. In this study, the authors conducted orbital MR scanning for 27 patients with Basedow disease, aged from 22 to 52, including 10 males and 17 females. Total of 54 eyes were measured, including both sides. Results showed that, average diameter and length of the extraocular muscles (in mm) were as follows: The superior group (superior rectus and levator palpebrae superioris) 5.44 + or - 2.40 and 42.23 + or - 1.58, inferior rectus - 6.88 + or - 3.25 and 44.65 + or - 2.72, medial rectus - 6.00 + or - 2.28 and 43.35 + or - 2.32, lateral rectus - 4.07 + or - 0.75 and 43.51 + or - 2.55, diameter of the superior oblique - 2.72 + or - 0.26. Overall diameter was 25.11 + or - 8.97. Mean eyeball position was 6.69 + or - 0.26.MRI proved to be the best diagnostic imaging method for orbital investigation with the high image resolution, multiplanar scanning and without artifact at skull base.