During a period of 18 years, 41 cases of congenital dilatation of the common bile duct in young patients (11 of them were less than 12 months of age) were treated at Bicetre Hospital. A retrospective analysis of these cases underline the following points. A close etiopathogenic relation exists between the presence of a common hepatico-pancreatic duct and a congenital dilatation of the common bile duct (in this study, 16 cases demonstrated the anomaly out of 20 cases for which the common bile duct could be analysed). Early surgical treatment must be undertaken before occurrence of liver complications (6 patients have cirrhosis when first treated, 4 of them were children less than 12 months of age). Abdominal echotomography (100% of preoperative diagnosis) and transparietal cholangiogram are the best investigations for providing pictures of hepatico-pancreatic abnormalities and collecting bile samples for bacteriological and chemical study. The treatment of congenital dilatation of common bile duct by cyst excision and Roux en Y hepaticojejunostomy has good long term results. After 20 cases of complete cyst excision, 6 of them were children under 12 months, and 17 cases or partial cyst excision respecting the cyst fundus when they were intraduodenal and retropancreatic in position (4 were children under 2 months) we have noted that 83% of these children had a good outcome with a mean follow up of 7 years. Complications include hepatico-jejunal stenosis at the anastomosis site in 2 patients, for which they were reoperated and cholangitis with hepatico-jejunal anastomosis in 6 cases. There were 3 deaths in children under 12 months who already developed hepatic cirrhosis and episodes of severe cholangitis when preoperative diagnosis was first proved. In conclusion, the future life of the majority of these children is expected to be uneventful inasmuch that bile stasis has been corrected, with resolution of inflammatory lesions which are known to expose to secondary malignancies of the biliary tract.