The aim of this study was to evaluate the usefulness of CD56-immunostaining using extrahepatic biliary tree (EHBT) specimens as a predictive factor in biliary atresia (BA). The staining intensity of CD56-stained specimens was scored in 13 children with BA as follows: 0 = no staining, 1 = weak staining, 2 = moderate staining, and 3 = strong staining. There was strong (score 3) staining of CD56 in the EHBT specimens of 4 patients with more than 1.5 mg/dl of serum total bilirubin in accordance with a decrease of jaundice. Weak staining of CD56 was seen in the EHBT specimens of patients with no or only one episode of postoperative cholangitis. Strong staining of CD56 was noted in the EHBT specimens of 4 patients who underwent liver transplantation. Our present findings support the possibility of discriminating between good and poor prognoses of clinical outcome after Kasai portoenterostomy.