THE REMARKABLE character and extreme rarity of idiopathic dilatation of the common bile duct (congenital choledochal cyst) render it a lesion of such interest as to justify the report of a single case. Shallow and Eger,1 in 1943, reviewed the subject and were able to collect only 175 well-authenticated cases from world literature. Their material was well organized and dealt with all phases of the condition so thoroughly that detailed discussion of the clinical features of the condition in this paper would be repetitious. Information gained from their work and additional isolated case reports and small series of cases since that time2 have helped to clarify the diagnosis and treatment of this lesion. Of considerable historical interest but not brought out in their paper was the fact that the first recorded successfully treated case was reported by Williams and Smithwick3 in 1929. The patient was a 5-year-old