Hilar cholangiocarcinoma is one of the most difficult tumors to stage and treat. This study aims to evaluate (1) the best diagnostic imaging, (2) the usefulness of preoperative biliary drainage, (3) the resectability rate, and (4) the results of palliative treatments and surgical resection. Seventy-six patients with hilar cholangiocarcinoma with a mean age of 64 +/- 11 years were treated at our institution from 1989 to 1999. Patients were studied preoperatively using ultrasound, computed tomography (CT), and percutaneous cholangiography or magnetic resonance cholangiography. Forty-eight patients (63%) underwent palliative treatment. Twenty-eight patients underwent surgical curative therapy; 20 resections and 8 orthotopic liver transplantations (OLTs). Percutaneous transhepatic cholangiography was performed in 18 of 28 patients (64%), and magnetic resonance cholangiography in 5 patients; both methods were equally effective in establishing tumoral invasion of the biliary ducts. Five patients did not undergo either diagnostic modality. Excluding the patients who underwent OLT, no significant differences were found in surgical mortality (1 v 2 patients) or postoperative morbidity (100% v 66%) for patients with and without preoperative biliary drainage. The postoperative mortality rate was 11% (3 of 28 patients). The overall resectability rate was 37%. Mean survival in the surgical and palliative groups was 35 and 6 months, respectively (P <.0001). Patients who underwent OLT had a better 5-year survival rate than those treated by tumor resection (36% v 21%; P =.02). Combined chemotherapy and radiotherapy apparently did not provide a significant survival benefit. Helical CT and magnetic resonance cholangiography are useful techniques to delineate tumor extent and rule out vascular invasion and lymph node or liver metastases. No clear conclusions regarding preoperative drainage can be drawn from this study. A high resectability rate (37%) is feasible with major hepatectomy.