In order to understand the mechanism of hepatic abnormalities appearing during total parenteral nutrition, biliary bile acid composition and liver function tests were examined serially in 15 patients undergoing total parenteral nutrition for inflammatory bowel disease. In all 12 patients who underwent duodenal intubation before initiation of total parenteral nutrition, lithocholic acid accounted for less than 1% of total biliary bile acids. After 11-22 days of total parenteral nutrition, lithocholic acid accounted for 7%-15% of biliary bile acids in 5 patients and less than 1% of biliary bile acids in 10 patients. In the 5 patients with elevated levels of biliary lithocholic acid, serum alkaline phosphatase and aminotransferase activities rose progressively at serial determinations, the increase being significant after 2 wk of total parenteral nutrition. These results suggest that lithocholic acid may be involved in the hepatic lesions observed in patients undergoing total parenteral nutrition.