Fifty-three patients with documented primary biliary carcinoma were studied with computed tomography. Twenty-six patients had gallbladder carcinoma and 27 patients had carcinoma of the biliary ductal system. Ninety percent of patients with gallbladder cancer had an intraluminal mass. Local invasion into the liver was common. The majority of patients with biliary ductal carcinoma had dilated bile ducts, while only 50% of patients with gallbladder cancer had biliary ductal dilatation. The most common location of tumor involving the extrahepatic biliary ductal system was the distal common bile duct. This occurred in eight patients out of 27, or 30% of the cases.