Intraluminal ultrasound with 12.5 and 20 MHz transducer allows precise analysis of the extrahepatic bile ducts and the adjacent structures. Inflammatory and malignant thickening of the bile duct wall can be assessed without difficulty. It is not possible, however, to differentiate between benign and malignant bile duct thickening, and for this purpose biopsy is required in addition. In tumor staging intraluminal ultrasound is superior to conventional ultrasound, because tumor infiltration into the adjacent tissues can be assessed and lymph nodes along the hepaticoduodenal ligament can be detected. Owing to the ultrasound frequencies available, local staging is limited to a circumference of 1.5/2 cm. Intraluminal ultrasound provides additional information that is useful in the diagnosis and therapy of bile duct stones and in different types of palliative tumor therapy. The procedure is simple and not too time consuming, and it involves no risks to the patient.