Sonographic findings of primary Budd-Chiari syndrome with membraneous obstruction of inferior vena cava (IVC) in seven cases, were evaluated and correlated with venographic findings and CT findings. In all cases, sonography showed highly echogenic membrane or segmental obliteration of the IVC with occlusion of hepatic veins. Additional sonographic findings were transhepatic collaterals, hepatomegaly, splenomegaly, ascites, and associated hepatomas. In comparison with venography, sonographic examination has advantages in delineation of extent of occlusion, nature of the IVC obstruction, and the simultaneous evaluation of adjacent organs. In comparison with CT, sonographic examination has advantages in evaluation of location of IVC obstruction, nature of obstruction, and extent of obstruction.