Computed tomography and real-time ultrasonography may not be conclusive for the diagnosis of the Budd-Chiari syndrome; in many cases more information may be needed, especially on vascular alterations. Doppler ultrasonography provides qualitative data on flow direction and pattern, thereby contributing significantly to diagnosis. Eight cases in which hepatic vein patency was unclear and presence of intrahepatic vessels resembling hepatic veins raised problems of interpretation in real-time ultrasonography are described. In some cases, patency or occlusion of the upper portion of the inferior vena cava were difficult to identify with real-time ultrasonography. Doppler ultrasonographic investigation showed flow in the hepatic veins to be completely absent in two cases and reversed in another two. In the remaining four cases, a flat waveform was evident. Flow in the inferior vena cava was reversed in four cases and showed a flat waveform in three other cases. Portal vein thrombosis was detected in only one case, whereas the remaining seven patients showed slow hepatopetal flow. These findings demonstrate that absent or reversed flow in the hepatic veins and/or flat flow in the hepatic veins associated with reversed flow in the inferior vena cava may be considered diagnostic for the Budd-Chiari syndrome. For this series the sensitivity of Doppler ultrasonography was 87.5%.