The natural history and pathways by which carcinomas of the gallbladder and extrahepatic bile ducts spread after attempted curative surgery offer a rationale for postoperative radiation therapy. We review: 1) the increasing use of primary-curative radiation therapy for these cancers, along with 2) the early results of innovative intraoperative irradiation and the transluminal insertion of radioactive sources into transhepatic catheters, 3) the efficacy of irradiation for metastases to the portahepatis, and 4) the overall effects of irradiation on the gallbladder and extrahepatic biliary system.