From 1983 to 1986, nine patients with advanced cancers of the proximal biliary tract were treated with intraoperative electron beam radiation therapy (IORT) following surgical resection or intubation. Five patients also received external beam radiation and four received chemotherapy. Early complications were minimal. Late complications included cholangitis, gastroduodenal ulceration, gastric outlet obstruction and portal vein thrombosis. Symptomatic recurrent or residual disease developed in eight patients with a median disease-free survival of 6 months. Seven patients failed locally; four recurred outside of the intraoperatively radiated field. The longest survivor is free of disease at 40 months; one patient is alive with disease at 30 months. Mean and median survivals were 16.8 months and 13 months respectively with 56 per cent 1-year survival. This was not different from a mean survival of 11 months and 46 per cent 1-year survival observed in 13 concurrent patients treated by external beam +/- 192Ir. Survival of six patients not treated by radiation was only 4.6 months (P = 0.3). Two thirds of patients had good or fair palliation. IORT has theoretical advantages for the treatment of locally advanced biliary cancer; preliminary results suggest useful palliation and potential long-term survival. Complications require ongoing evaluation and superiority to conventional treatment modalities has not been demonstrated.