The relapse of icterus may be a sign of serious postoperative complication after hepatic portoenterostomy for biliary atresia. To analyse the cause of such icteric flare-up, a retrospective study was made on 27 patients. A total of 38 episodes of icteric flare-up occurred in 19 patients. An accompanying disease, which had not directly involved the biliary tract, was assumed to be the cause in 11 episodes (29%). Fourteen episodes (37%) were due to biliary tract infection caused by the cyst formed at the porta hepatis (5 episodes) or so-called ascending cholangitis (9 episodes). The other 13 episodes (34%) were free from both accompanying disease and signs of biliary infection. Among them, the cause of icteric flare-up was the cyst at the porta hepatis in one episode, scar tissue formation at the porta hepatis in 9 episodes and undetermined in 3 episodes.