In spite of many reports which suggested the efficacy of chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA) on cholesterol gallstone dissolution, problems still remain to be solved, such as the ideal dosage and duration of treatment to obtain maximal benefit with minimal untoward effects. The author reports in this paper a comparative study on changes of bile acid level and lipid composition in blood and bile during the clinical course after initiation of CDCA and UDCA therapy in effectively and ineffectively responding groups of patients with cholesterol gallstones in the gallbladder.