We studied intrahepatic bile ducts of five patients with chronic ulcerative colitis and primary sclerosing cholangitis. The livers had been obtained at the time of orthotopic liver transplantation. After specimen cholangiography and perfusion fixation, sequential blocks and sections from portal tracts were studied, combining light microscopy with scanning electron microscopy. In vivo cholangiograms were studied also. The specimens revealed: (i) absence of normal bile ducts; (ii) presence of thin-walled tubular or saccular cholangiectases with semicircular and annular fibrous crests, without evidence of superinfection; (iii) cholangiectases with secondary acute or chronic-cellular cholangitis, with or without cholangitic abscesses; (iv) fibrous cholangitis without ductal dilatation; (v) transformation of bile ducts into fibrous cords which were either solid or contained remnants of bile duct epithelium, and (vi) complete loss of bile ducts. The shape and distribution of the cholangiectases suggested that these lesions were manifestations of the disease process and not passively dilated normal ducts. Fibrous-obliterative cholangitis with formation of fibrous cords was found not only at the level of interlobular and adjacent septal bile ducts but also at the level of segmental bile ducts that normally would have been demonstrable in cholangiograms. The “pruned-tree” appearance in cholangiograms appears to result from the transition between patent and often cholangiectatic ducts, and duct obliteration. At present, intrahepatic cholangiectases in association with duct obliteration can be considered pathognomonic morphologic features of primary sclerosing cholangitis.