The purpose of this study is to determine the causes of lithogenic bile in patients with gallstones and to develop and evaluate methods for transformation of lithogenic into normal bile. This study will be an extension of our recent investigations on the pathogenesis of lithogenic bile in American Indian women; it will be concerned primarily with causes of lithogenic bile in the white population. Methods will include those developed by the principal investigator for the study of cholesterol and bile acid metabolism in man. The methods are the cholesterol balance method and an intubation technique for quantifying hepatic secretion of biliary lipids. These methods enable us to estimate hepatic secretion rates for cholesterol, bile acids, and phospholipids, and also to determine the causes for abnormal secretion rates. Secondly, several techniques for transforming lithogenic into normal bile will be examined. These will include the administration of bile salts (cholic and chenodeoxycholic acid), phenobarbital, weight reduction, and low fat, low cholesterol diets.