BACKGROUND AND OBJECTIVES Hilar cholangiocarcinoma is a morbid disease with a poor prognosis because resection cannot be performed in many cases. The purpose of this study was to evaluate whether external beam radiotherapy (RT) combined with expandable metallic biliary stent (EMS) affects the length and quality of survival of patients with unresectable hilar cholangiocarcinomas. METHODS Fifty-one patients with unresectable hilar cholangiocarcinoma were retrospectively reviewed. Thirty patients received external beam radiotherapy combined with EMS (EMS+RT group), 10 patients were treated with EMS alone (EMS group), and the remaining 11 patients underwent percutaneous transhepatic biliary drainage alone (PTBD group). The length and quality of survival were analyzed and compared among the three groups. RESULTS The mean survival of 6.4 months in the EMS group was significantly longer than that of 4.4 months in the PTBD group (P < 0.05). The EMS+RT group with a mean survival of 10.6 months had a significantly longer survival than the EMS group (P < 0.05). The average of the monthly Karnofsky scores of 74.9 in the EMS+RT group and 68.1 in the EMS group, as a parameter of quality of survival, was significantly higher than that of 57.7 in the PTBD group (P < 0.01). The number of hospital days per month of survival was significantly smaller in the EMS+RT and EMS groups than in the PTBD group (10.4, 14.2 vs. 27.3 days; P < 0.001). The EMS+RT group had a longer stent patency than the EMS group (mean: 9.8 vs. 3.7 months; P < 0.001). CONCLUSIONS These results indicate that external radiotherapy combined with metallic biliary endoprosthesis can increase the length and quality of survival and consequently provide a definite palliative benefit for patients with unresectable hilar cholangiocarcinoma.