Preoperative cholangiography and angiography have been used in a series of 37 patients with hilar cholangiocarcinoma investigated over a 17-month period in a single specialist unit. Twelve lesions were judged to be irresectable on the basis of the cholangiographic findings: this was confirmed at laparotomy in nine patients and at autopsy in one. Angiography was performed in 21 patients, and suggested irresectability in eight: this was confirmed by laparotomy in seven. The eighth patient had compression of the left portal vein which had been interpreted as tumor invasion on angiography, and it was possible to perform a curative extended right hepatic lobectomy. Of the 13 potentially resectable patients, three were unfit for major resectional surgery. Five were found to be irresectable at laparotomy because of vena cava involvement in two and distant metastases in three. Five patients underwent resection with histologically clear margins. The combined use of cholangiography and angiography is recommended as a means of selecting appropriate therapy for patients with hilar cholangiocarcinoma.