There are two major bile acids, cholic acid and chenodeoxycholic acid, which are synthesised in the hepatocyte by the cytochrome P450-mediated oxidation of cholesterol. These bile acids are secreted into the biliary canaliculi as sodium salts and conjugated with glycine, taurine, sulphate or glucuronic acid, and stored in the gall bladder until excreted into the intestinal lumen in response to a fatty meal. Enterohepatic circulation of bile salts is associated with conversion of the primary bile salts to seconday bile salts by bacerial enyzmes. The total bile pool of about 4 grams is recirculated about 5 to 10 times per day. Because serum bile salt concentration can increase by two to five times after a meal it is important that bile salts are measured while the subject is fasting.