A simple immunofluorescence test for antibody to a mitochondrial antigen present in many tissues is a reliable method of distinguishing most cases of primary biliary cirrhosis from jaundice due to extrahepatic biliary tract obstruction. Of 30 cases diagnosed as primary biliary cirrhosis, 26 had antimitochondrial antibody whereas none of 77 cases with jaundice due to extrahepatic bile duct obstr...