One hundred randomly selected sonograms were retrospectively reviewed to determine the accuracy of employing the margin characteristics of intrahepatic venous radicals to distinguish portal from hepatic veins; 99% of intrahepatic portal veins demonstrated high amplitude acoustic margins. However, one or more hepatic veins also had high amplitude acoustic margins in 29% of patients in whom intraparenchymal hepatic veins were identified. The authors conclude that an intrahepatic venous structure without an echogenic border is almost invariably an hepatic vein, although other anatomical features should be considered for proper classification of intrahepatic venous structures which demonstrate high amplitude echoes surrounding the lumen.