【Abstract】Objective To observe the bacteria in cholesterol stones by electronic microscope and to explore the role of bacteria in the stone formation.Methods Twelve patients with cholelithiasis underwent operations (male 6, female 6, average age 54.6 years） with cholecystolithiasis 5, extrahepatic and intrahepatic bile duct stone 1, common bile duct stone combining with gallstone 6. The cholesterol stones were observed by electronic microscope.Results There were bacterial structures in the cholesterol stones and cholesterol crystals.Conclusion There are bacteria in the core and peripheral of cholesterol stones, which suggests that bacteria may play an initial role in the formation of cholesterol stones.