DNA ploidy analysis of 22 lesions arising from the intrahepatic and extrahepatic biliary systems and gallbladder was performed on Feulgen-stained 5-pm sections from archival paraffin-embedded tissue on an image analyzer (CAS-200). The cases included intrahepatic cholangiocarcinoma (n = 6 ) , extrahepatic bile duct carcinoma (n = 5), carcinoma of the gallbladder (n = 1 l), and appropriate controls. All malignancies were stage 111 and IV adenocarcinomas with the exception of 1 stage II moderately differentiated gallbladder adenocarcinoma. No correlation with ploidy and stage could be made, most likely because of the advanced stage of the tumors at the time of presentation. When DNA ploidy was compared with the grade of alignant tumors of the intrahepatic and extra-M hepatic biliary systems are highly lethal malignancies in large part because they are advanced at the time of presentation. Carcinoma of the gallbladder is the more common of these malignancies. Gallbladder carcinoma typically has a 5-year survival less than 5%'; exceptions to this are well-differentiated tumors confined to the mucosa.2 Patient mortality is also common within the first 12 months in unresected cholangiocarcinoma of the extrahepatic bile ducts.3 Cholangiocarcinoma of the intrahepatic biliary system represents a small portion of all primary liver cancers (2.6%-35.5%)4 with survival statistics also usually listed in months (average sunival, 7.2 months).4 Tumor stage is the most reliable prognostic indicator in biliary malignancies.'X2 DNA ploidy studies have not been shown to be independent prognostic indicators in carcinoma of the gallbladder,1,2 and, to our knowledge, have not been performed in cholangiocarcinoma of the liver or adenocarcinoma of the extrahepatic biliary system.