Previous investigations have shown that cicloxilic acid, a hydrocholeretic drug, lowers bile cholesterol saturation without interfering with the intestinal absorption of cholesterol as well as with the hepatic synthesis of both cholesterol and bile acids. The mechanism whereby cicloxilic acid antagonizes lithogenic bile secretion is still unknown. However, most evidence favors the view of a relationship between choleretic and antilithogenic effects of the drug. To test this hypothesis the effects of a single oral dose (240 mg) of cicloxilic acid on bile flow and biliary lipid excretion rates have been examined in four nonobese cholecystectomized patients with balloon-occludable, reinfusion T-tubes. The results indicate that cicloxilic acid exerts a marked choleretic effect combined with a reduced output of bile cholesterol and an increase in bile acid excretion. Bile cholesterol saturation significantly decreases 90 min after cicloxilic acid in respect to control value. These data provide evidence of a link between choleretic and antilithogenic effects of cicloxilic acid and suggest its usefulness in the treatment of bile cholesterol supersaturation.