The effect of intravenous administration of cholic acid on sphincter of Oddi (SO) and gallbladder motility was studied. Bolus doses of cholic acid, 20 to 60 mg/kg, produced inhibition of SO wave frequency, a fall in gallbladder pressure, and enhanced bile flow. However, hydrocortisone, 10 and 20 mg/kg, produced comparable elevation in bile flow with no effect on SO and gallbladder motility. The effect of cholic acid on SO motility was not influenced by prior treatment with atropine. Phentolamine or propranolol administration did not influence SO wave frequency, but subsequent injection of cholic acid resulted in a decrease in SO wave frequency. Gallbladder pressure was not influenced by atropine, phentolamine, or propranolol, and these agents did not influence the cholic acid-induced fall in gallbladder pressure. These findings suggest that bile acids influence the motility of the biliary tract.