BACKGROUND/AIMS: Palliative endoscopic or percutaneous internal drainage is widely used for treating hilar cholangiocarcinoma. Yet unilateral biliary drainage does not completely improve jaundice and it can induce acute cholangitis by the undrained contrast media. To investigate this technique's technical and clinical effectiveness, a newly devised Y-configured dual stent was used for treating advanced hilar malignancies. METHODS: From May, 2005 to May, 2007, 20 hilar malignancies (men: women=9:11, age=70.5 yr) that were not suitable for surgical resection were included in this study. For bilateral metal stent placement, a biliary stent with a wide open central mesh was first inserted. After this, another stent without a hole was inserted into the contralateral hepatic duct through the open central mesh of the first stent. RESULTS: Bilateral metal stent insertion was done in 14 of 20 patients. Among the 14 patients in whom bilateral stents were successfully placed, the rate of functional success was 100%. There were no early complications. As a late complication, stent occlusion occurred in 4 of 14 patients (28.5%), and one of these patients had a plastic stent inserted. The other 3 patients were treated with percutaneous transhepatic biliary drainage. The median stent patency period was 231 days. CONCLUSION: The bilateral metal stent method using the Y stent is safe and effective for bilateral biliary drainage in patients with unresectable hilar malignancies.