Early prognosis factors determination is an important objective after Kasai's operation for biliary atresia repair. Serologic test, postoperative biliary flow, histologic studies and clinical manifestations provides adjunctive information. Hemodynamic patterns in biliary atresia where described in 80's before liver transplantation. This preliminary report evaluates portal flow velocity, hepatic arterial resistance and portal calibre in these patients. A prospective sonographic investigation was performed in ten children with biliary atresia. Hemodynamic findings and hepatobiliary function were compared in order to establish prognosis. All our patients with good prognosis had hepatopedal portal flow greater than 14 cm/sg, and arterial resistance between 0.68-0.78. Four patients with poor prognosis had hepatopedal flow lesser than 14 cm/sg or hepatopedal flow an resistance in hepatic artery was greater than 0.80.