Endoscopic endoprosthesis insertion plays an increasingly important role in the palliation of jaundice in patients with unresectable malignant hilar biliary obstruction (HBO). Drainage of both obstructed lobes in Types II and III HBO is not necessary to achieve adequate palliation, providing 25% of the liver volume is drained by a single endoprosthesis. The anatomy of the main hepatic ducts suggests some benefit may accrue from preferential drainage of the left hepatic duct. We have reviewed a consecutive series of 151 patients with Type II and III HBO over a 4-year period to compare the outcome of endoprosthesis placement in either the right (RHD) or left (LHD) hepatic duct, to test this hypothesis. No significant difference was found in terms of successful drainage, complications, 30-day mortality, number of endoprosthesis changes and survival between patients with right system drainage compared with those with left sided drainage (chi 2-test and Mann Whitney U test). When dealing with a patient with a Type II or III HBO, we would recommend single endoscopic endoprosthesis insertion into the technically most accessible obstructed system. This would achieve adequate palliation in 84% of the patients.