1. A new concept of the etiology of choledochal cyst is presented. The etiology of this entity is based on an anomalous relationship between the common bile duct and the pancreatic ducts.2. This anomaly allows reflux of pancreatic juice into the common bile duct. Pancreatic juice leads to cholangitis and dilatation of the common duct.3. The roentgenographic evaluation of choledochal cyst with special emphasis on cholangiography is presented.4. The surgical implications of this anomaly are suggested.