AbstractExtrahepatic biliary carcinomas occurred in 2 Asiatic bears at the National Zoological Park in Washington, D.C. The tumors were associated with ascites in both cases and jaundice in 1 and metastasized widely. Neither bear had gallstones. Microscopically, the tumors were infiltrative, scirrhous adenocarcinomas that produced varying amounts of mucin. A genetic predisposition and change from the natural diet were factors proposed to contribute to the development of this neoplasm.