The histology of the common bile duct was studied in 45 patients with choledocholithiasis and/or papillitis and compared with a control group of ten cadavers without hepatic or biliary disease. Choledochitis was diagnosed in 44. Only one patient presented a histologically normal duct. The inflammatory process was characterized by proliferation of connective tissue and loss of elastic fibers, cellular infiltration of lymphocytes and polymorphonuclear leukocytes, and atrophic dilatation or hyperplasic glandular changes. Choledochitis was divided in two types: chronic and acute-chronic, and according to the intensity of the inflammatory process was also classified in slight, moderate or severe. No correlation was found between choledocholithiasis and/or papillitis and type and intensity of choledochitis.