BACKGROUND AND AIMS: It is necessary to study about extrahepatic bile duct (EHD) lesions in cases with abnormal liver function test (LFT) and clinical symptoms, even though abdominal ultrasonography could not find out the bile duct lesions. It is unclear however, whether the precise examination of EHD lesions are necessary in asymptomatic patients with normal liver function showing EHD dilatation without any lesions on abdominal ultrasonography (US). METHODS: We examined prospectively about EHD using endoscopic ultrasonography (EUS), followed by endoscopic retrograde cholangiopancreatography (ERCP) in fifty-three patients with normal LFT showing only EHD dilatation on US. The mean EHD diameter on US was 9.1 1.4 mm. RESULTS: The EHD dilatations alone on EUS were 41.5% and the EHD dilatations with lesions were 58.5%. The observed lesions of EHD by EUS were bile duct stones in 32.1%, thickening or stricture of distal bile duct in 17.0%, ampullary mass in 5.7% and CBD polyps in 3.8%. Three cases of ampullary mass were confirmed as 2 cases of T1 ampullary cancer and 1 case of papillitis. Examination by ERCP revealed EHD dilatation alone in 49.1% and bile duct lesions in 50.9%. ERCP could not detect the 2 cases of CBD polyp and 2 cases of distal bile duct thickening. CONCLUSIONS: In patients with normal LFT showing only EHD dilatation on abdominal US, EHD lesions can be detected in high frequency. Therefore, further examination about dilatated EHD should be conducted and for this purpose, EUS is be recommended as a useful tool.