Congenital dilatation of the common bile duct (choledochal cyst) is a rare entity. The most complete reviews of this subject are those of Shallow et al1 with 175 cases in 1943, Tsardakas and Robnett2 with 232 cases in 1956, and the recent one of Alonso-Lej et al3 with 403 cases in 1959. Alonso-Lej et al3 stated that one third of the cases were reported by Japanese authors. This indicates that orientals are particularly affected. It is generally agreed that this condition is congenital in origin. There are numerous theories proposed to explain the embryological condition. The theory that seems most plausible and explains the greatest number of cases is that of Yotsuyanagi.4 According to Yotsuyanagi,4 the etiology is an inequality in proliferation of the epithelial cells at the stage of development in which the primitive choledochus is still solid. If, at the same stage,