Six normolipidemic and six hypertriglyceridemic subjects were studied. The investigations were conducted before and after the basal diet (cholesterol intake about 0.8 mmol/day) was replaced by a cholesterol-rich diet (cholesterol intake about 4 mmol/day). Irrespective of the type of diet, the combined formation of cholic acid (C) and chenodeoxycholic acid (CD) was about two times higher in the hyperlipoproteinemic (mostly type IV) than the normolipidemic subjects. With the cholesterol-rich diet, the total plasma cholesterol increased in all normolipidemic and in four hyperlipidemic patients. Although total bile acid formation remained constant, there were several indications that an augmented intake of dietary cholesterol influenced bile acid metabolism. The pool size of CD increased in all but one normolipidemic subject. This group also displayed a decrease in the C/CD ratio of the bile acids produced and in the C/CD ratio of the bile acids in duodenal bile. The latter finding was also encountered in the hyperlipoproteinemic patients. On the basis of these and other data, it is suggested that the pattern of the bile acids synthesized may roughly reflect the degree of hepatic cholesterogenesis. Cholesterol feeding had no consistent effects on the molar cholesterol concentration in duodenal bile.-Andersén, E., and K. Hellström. The effect of cholesterol feeding on bile acid kinetics and biliary lipids in normolipidemic and hypertriglyceridemic subjects.