B-ultrasonography and/or CT scannings of 84 cases of enlarged superior ophthalmic vein (SOV) were analysed morphologically and etiologically. Carotid-cavernous fistula, ophthalmic Graves disease, Tolosa-Hunt syndrome, orbital vascular deformity, inflammation at the apex of the orbit, orbital pseudo tumor, intraorbital hematoma and thrombosis of the SOV might induce enlargement of SOV. Associated with other Findings of intraorbital tissues revealed by CT and B-ultrasonography, the etiological diagnosis of the enlarged SOV could be made. The dynamic findings of the SOV rendered by B-ultrasonography and Doppler ultrasonic play an important role in the diagnosis of carotid-cavernous fistula.