Histometric examinations, based on the assumption that hepatic arterial branches and bile ducts run parallel within the portal tracts, suggest that in primary biliary cirrhosis bile ducts with a lumen (the smallest diameter between the subepithelial basal membranes) below 70--80 micron are destroyed. The smaller the ducts, the more they destroyed. Extensive destruction of the ducts was seen more frequently in the nonfibrotic stage of primary biliary cirrhosis than in later stages. Serial sections of the intrahepatic bile ducts in primary biliary cirrhosis revealed three types of periductal lesions preceding the disappearance of bile ducts: (A) periductal cellular reaction including features of chronic nonsuppurative destructive cholangitis, (B) periductal edema, and (C) periductal fibrosis. In the nonfibrotic stage, types A and C were frequent, whereas in the fibrotic stage types A and B were increased, and type C was predominant in the cirrhotic stage.