Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) share many clinical and pathologic features. Central to the symptoms and biochemical alterations of both conditions is a substantial loss of intrahepatic bile ducts, leading to interference with bile flow. This pathologic change may ultimately result in cirrhosis of the biliary type. In addition, however, biopsy specimens usually show an element of liver-cell destruction and associated inflammation, mainly interface hepatitis. This finding is more pronounced in PBC than in PSC but can lead in both diseases to features that resemble those of cirrhosis as a result of hepatitis virus infection. The resemblance often leads to diagnostic confusion, which is easily overcome by attention to the clinical, radiologic, serologic, and biochemical context. Histologic staging of PBC and PSC has led to a greater appreciation of their evolution but is hampered in biopsy material by sampling error. Examination of explanted livers at transplantation has demonstrated a wide variation in the maturation of lesions in various parts of the organ.