In the presentation of a case of traumatic rupture of a congenital cyst of the choledochus, we believe that we are reporting a case unique in medical history. We have found, after a rather careful search of the literature, reports of only 130 accepted true cases of congenital cyst of the choledochus, and in none of these was there a history of traumatic rupture. Wright,1 in reporting a case of cyst of the choledochus diagnosed by roentgenographic examination, made only casual mention of another of his cases in which the patient died from rupture of a congenitally dilated common duct after a fall from a bicycle, but this case has not been recorded elsewhere in the literature. Over a period of twenty years, Judd and Greene,2 of the Mayo Clinic, found only one cyst of the choledochus in a series of 17,381 consecutive operations on the bile duct.