In 37 children with extrahepatic biliary atresia between 12 days in 9 years of age we performed 72 duplexsonographic examinations of the portal system and the hepatic artery. In the control group we investigated 61 healthy children. All investigations were performed with computer sonography (Acuson 128) with a 3.5 MHz and 5 MHz-Transducer. We described changes of sonographic parameters such as hepatic structure, liver and splenic size. In 14 children with extrahepatic biliary atresia hepatofugal collaterals were visible. Specially in patients with collaterals we found changes of vessel diameters. The maximal flow velocity of the portal vein was significantly decreased in patients with extrahepatic biliary atresia.