Two adults with communicating cavernous ectasia of the biliary tract (Caroli disease) are described. Both patients had the pure form of the disease, characterized by saccular dilatation of intrahepatic bile ducts, multiple intrahepatic calculi, absence of portal hypertension, and associated cystic renal disease. Computed tomographic (CT) scans of the liver showed tiny dots with strong contrast enhancement within dilated intrahepatic bile ducts (the central dot sign). These intraluminal dots on CT scans corresponded to intraluminal portal veins on sonograms, findings indicating portal radicles surrounded by dilated intrahepatic bile ducts.