The preoperative diagnostic approach in 25 patients with bile duct carcinoma was studied. Investigation procedures included gray-scale ultrasonography with guided fine needle biopsy of focal lesions, percutaneous transhepatic or retrograde cholangiography, transhepatic biliary drainage with brush and forceps biopsy of biliary stenosis as well as selective angiography for feasibility of surgical resection. Diagnosis was ensured in 23 patients by cytologic or histologic tissue specimens. Twenty-one lesions were judged unresectable on the basis of bile duct or vascular tumor extension and patient status. These patients were treated either by iridium 192 wire radiation therapy (6 cases) or by nonsurgical biliary drainage. Four patients with a potentially resectable tumor underwent surgery. This preoperative diagnostic approach can be recommended for selecting appropriate therapy in patients with bile duct carcinoma.