Cholelithiasis is defined as the presence of stones within the lumen of the gallbladder or in the extrahepatic biliary tree. Cholecystitis, secondary to gallstones, is a common surgical disorder in Korea. Detailed microscopic descriptions, particularly the ultrastructural changes, of these diseases were not available. The goal of this study was to identify the ultrastructural alterations of gallbladder epithelium in cholecystitis with and without a stone, according to the degree of severity of inflammation, and the nature of the stone. The gallbladders of the control group, and cholecystitis cases without stone and with stone were fixed and examined with routine stain, special stain, immunohistochemical stain and trans-mission electron microscopy. The number and the volume density of the mucin containing secretary granules were not significantly increased in the calculous cholecystitis cases compared with those of the acalculous cholecystitis cases. Major findings were that the calculous cholecystitis cases showed a markedly reduced total lysosome area and volume density of the lysosome compared with those of the acalculous chole-cystitis cases. The differences between the mucin secretary granules and lysosomes, according to the degree of severity of cholecystitis and the natures of gallstones, were statistically not significant.