Ultrasonography is a predominantly accurate, relatively simple unique method of obstructive jaundice. The ultrasonographic findings of obstructive jaundice are dilated intra-and extrahepatic duct with intraluminal hyperreflective echo or mass in and/or around the bile duct. The superiority of high resolution real time ultrasonography for the diagnosis of obstructive jaundice is based on the easy detectability of extra-and intrahepatic bile ducts by its multiple sectional images in a short time, the flexibility of probe and the small srystal size. Author evaluated real time sonographic finding 46 obstructive jaundice patients confirmed by surgery or radiographical examinations. The results were: 1. Diameter of extrahepatic duct in obstructive jaundice were varied from normal to 4.0 Cm, mostly 8 to 10 mm in diameter(26%). Degree of dilatation of biliary duct appeared more prominent in cancer patients than any other causes of obstruction. 2. The site of obstruction was detected in 85% (39/46) and its common site was common bile duct in 63% (29/46). 3. The diagnostic accuracy of choledocholithiasis and cancer was 82% (22/27) and 44% (4/9), respectively. Diagnostic accuracy of the real time ultrasonography in obstructive jaundice was over all 75% (34/46).