In the diagnosis of tumor induced bile duct obstruction, ultrasonography is widely used procedure for evaluation of the biliary obstruction, because ultrasonography is non-ionizing, generally less expensive, and ofen more readily available. We analyzed 103 cases of confirmed extrahepatic bile duct obstruction by the tumor. The results were as follows: 1. Causes of tumor induced biliary obstructions were pancreas head carcinoma in 33 cases, bile duct carcinoma in 29 cases, gallbladder carcinoma in 16 cases, metastasis in 12 cases, hepatoma in 7 cases and ampulla ov Vater carcinoma in 6 cases respectively. 2. In the bile duct carcinoma, gallbladder carcinoma, hepatoma and metastasis, the obstructions of bile dute were frequently observed in the porta hepatis and common hepatic duct, pancreas head carcinoma in common bile duct, ampulla Vater carcinoma in ampullary portion. 3. The degree of dilatation of bile duct was more severe in distal obstruction. 4. sonographic demonstration of obstructed end were possible in 83 cases (80.5%). 5. The focal tumor masses were demonstrated sonographically in 68 cases (66.0%). In the gallbladder and pancreas head carcinoma the tumor masses were large and frequently observed sonographically. 6. The accuracy of sonography in the diagnosis the level of obstruction was 69.9%. The overall accuracy for specific diagnosis was 66.9%.