Membranous obstruction of the hepatic inferior vena cava(MOVC) is one of the common causes of Budd-Chiari syndrome. The aim of this study is to ascertain and compare the characteristic sonographic and CT findings of Budd-Chiari syndrome caused causes by MOVC. We studied 10 patients of Budd-Chiari syndrome caused by MOVC through sonography and CT. MOVC was confirmed by operation and/or inferior vena cavography. The cases included 9 men and one woman. With sonography, IVC obstruction was diagnosed in 9 cases. The cause of IVC obstruction was web in 5 cases and fibrous cord in 3 cases. The cause was unspecified in one case. Obliteration of the hepatic veins and inteahepatic collateral vessels were delineated in 9 cases. With color doppler sonography, the directions of blood flow of the hepatic veins through the intervenous communication were fairly well demonstrated in all 5 cases. With CT, IVC obstruction was diagnosed in 7 cases. The obliteration of the hepatic segment of the I C were segmental in 6 cases and diffuse in one case. CT demonstrated communicating vessels between the hepatic veins in 3 cases. Furthermore, systemic collateral vessls (azygos and hemiazygos veins, veins along the aabdominal wall, and internal mammary veins) were demonstrated in all cases. Liver cirrhosis was combined in all cases and hepatoma developed in 4 cases. Sonography us useful to detect the MOVC and to demonstrate hepatic venous obstruction and intrahepatic collateral vessels. Color deppler sonography is easily performed to show the direction of the blood flow through interconnectiong vessels. CT shows the obliterated segment of the IVC clearly and multiple prominent systemic collaterals. In conclusion, Budd-Chiai syndrome caused by MOVC is accurately diagnosed by combined color doppler sonography and CT.