The diagnostic value of ultrasonography and percutaneous cholangiography was compared in 114 consecutive patients with obstructive jaundice. The final diagnosis was obtained by surgery or autopsy. Transhepatic cholangiography diagnosed obstruction and its level in all patients, whereas ultrasonography failed to find obstruction in 3 patients and was unable to determine the level in 11 patients. The cause of obstruction was correctly assessed in 106 patients by transhepatic cholangiography and in 74 by ultrasonography. In 15 patients with obstruction caused by common duct calculi ultrasonography only diagnosed the five, and in 9 patients malignant obstruction was diagnosed as calculi. Ultrasonography is a reliable tool for diagnosis of obstructive jaundice and in most cases for localisation of the level of the obstruction. However, diagnosis of the cause of obstruction and of its precise topography requires direct cholangiography.