Abstract: Objective: To evaluate the clinical value of intracavitary radiotherapy with a sealed source of 125I for treating extrahepatic cholangiocarcinoma. Methods: Thirteen patients with extrahepatic cholangiocarcinoma were diagnosed by endoscopic retrograde cholangio-pancreatography (ERCP)and were treated with endoscopic retrograde biliary drainage (ERBD). The cholangiocarcinoma position and area were ascertained and the outline of the shape and size of the cancerous focus were finalized.The 125I particles were then implanted into the focus using the applicator. Results: In the 13 cases,the 1-year survival rate was 100% (13/13) and the 2-year survival rate was 80% (4/5). The median survival time was 18 months. The longest survival time was 31 months. All patients are still alive except for one patient who died 16 months after treatment due to an abscess on the right lobe of the liver that led to right thoracic empyema. Symptoms of nausea, vomiting and leucopenia, as well as post-treatment complications of hemobilia and perforation of the bile duct were not seen in these cases. Total bilirubin was decreased to 9.0~36 μmol/L weeks after placement of the ERBD tube. Conclusion: The surgical procedure for using 125I brachytherapy for treatment of extrahepatic cholangiocarcinoma is minimally invasive, the treatment effects are significant, and there are limited side effects and complications. This technology should be popularized as a treatment for cholangiocarcinoma.