In a retrospective study of 30 patients with Graves' ophthalmopathy and 25 patients with exophthalmus due to other causes the patterns of ocular motility disturbances and the CT-findings were reviewed. In Graves' ophthalmopathy motility disturbances were found in 83% of the patients, in the control group 26% of the patients showed abnormal ocular motility. Enlarged eye muscles were found in 46% of the patients with Graves' ophthalmopathy and enlargement of the medial rectus muscle was the most consistent finding (42%). A clinical correlation was made between the severity of eye movement restriction and the appearance of the muscle on CT-scan.