A Roux-en-Y portoenterostomy (Kasai I) is performed for biliary atresia in a 12-week-old child. Emphasis is placed on the techncal aspects of the dissection in the porta hepatis, particularly the dissection cephalad to the portal vein bifurcation. Cholangiography, identification of the "sweet spot", division of the fibrous biliary remnant, and the technical aspects of anastomosis in the porta hepatis are detailed.