Light and electron microscopy were employed for evaluation of hepatic biopsies (9 puncture and 3 operative) to study morphologic changes in small bile ducts and lobular parenchyma in primary biliary cirrhosis (PBC). Altogether 12 female patients with PBC stage I and II and aged 36-59 were examined. Immune cytolysis of biliary epithelium indicative of delayed-type hypersensitivity is shown to underlie destructive cholangitis. The appearance of the canals between hepatocytes of the hepatic plate which connect biliary capillaries with perisinusoidal space evidence for impairment of hepatic lobular parenchyma. Cholemia and absence of hepatic cholestasis in PBS stage I may be due to bile capillary drainage into the hepatic sidusoids along these newly originated intercellular canals.