Rupture is one of the rare complications of choledochal cysts. The cause of rupture is unknown in many cases and is considered to be spontaneous. Two patients admitted to the hospital with acute abdominal picture were initially thought to have postoperative abscess and appendicitis. However, the presence of bilelike fluid suggested a bile tract pathology, and evaluation showed ruptured choledochal cysts. Although spontaneous rupture of a choledochal cyst is a rare complication, and can sometimes be the initial manifestation of a choledochal cyst, it should be considered in the presence of bilelike fluid and differentiated from spontaneous perforation of the bile tract. In spontaneous rupture of choledochal cyst, cystectomy, cholecystectomy, and Roux-Y hepaticoportoenterostomy is the treatment of choice. Copyright (C) 1997 by W.B. Saunders Company.