ES was performed preoperatively in 39 patients with a proximal bile duct carcinoma. The results were correlated with the histologic findings of resected specimens or intraoperative excision according to the new (1987) TNM classification. ES was accurate in assessing the depth of tumor infiltration. The overall accuracy of ES was 83.8%. Overstaging of T2 carcinoma occurred in three of ten patients (30%) and understaging of T3 carcinoma occurred in 3 of 27 patients (11%). ES was helpful in diagnosing lymph node metastasis (accuracy, 92.9%) but not accurate in defining nonmetastatic lymph nodes (accuracy, 18.8%). Difficulties occurred in distinguishing inflammatory lymph nodes and micrometastatic lymph node involvement. ES was not accurate in diagnosing hepatic metastases and peritoneal dissemination because of the limited penetration depth of ultrasound. The incidence of lymph node metastasis of advanced stage carcinoma was approximately 40%. Technical improvements, such as reduction of the diameter of the echoprobe, easy handling of ES-guided cytologic puncture, and the routine use of a catheter echoprobe during ERCP will further enhance the accuracy of E