1. The duodenal bile acid composition was analysed in 24 control subjects and 107 patients with various types of hyperlipoproteinaemia. A highly significant negative correlation was observed between the proportions of deoxycholic acid and cholic acid as well as between deoxycholic acid and chenodeoxycholic acid. Patients with gall-bladder disease had an increased proportion of deoxycholic acid in their bile.
2. Eight control subjects were studied before and during the ingestion of 1·9 mmol (0·75 g) of deoxycholic acid daily. In these subjects a rise in the proportion of deoxycholic acid was also accompanied by a fall in the proportion of both cholic acid and chenodeoxycholic acid in duodenal bile.
3. The biliary lipid composition and cholesterol saturation was determined before and during the administration of 1·9 mmol (0·75 g) of chenodeoxycholic acid (n = 12) or deoxycholic acid (n = 8) daily for 3–4 weeks. The cholesterol saturation was decreased during the chenodeoxycholic acid ingestion whereas no change occurred in bile saturation during deoxycholic acid administration.
4. Ingestion of chenodeoxycholic acid lowered serum triglyceride and deoxycholic acid lowered the serum cholesterol.