The protective effect of alcohol against cholesterol cholelithiasis has been established in several epidemiologic studies. An impairment of gallbladder motility in gallstone disease has been demonstrated in animals and in man. At a daily dose of 39 g, alcohol reduces the lithogenic index of bile, but its effect on gallbladder motility is still debated. To test this potential mechanism, the effect of 20 g of alcohol on gallbladder motility was studied, using an ultrasonographic ellipsoid method in 16 healthy male subjects. The stimulus for gallbladder contraction was a Lundh test meal. Using a cross over method, this meal was ingested by each subject once with water and once with alcohol. A third set of measurements was taken in each subject after ingestion of a Lundh meal and water to test the reproducibility of the sonographic method. The gallbladder kinetics were studied for 90 minutes following ingestion of the test meal and beverage. Alcohol stimulated rapid post prandial gallbladder emptying, and accelerated gallbladder filling. This second action could result from sphincter of Oddi pressure enhancement and, perhaps, decrease of gallbladder absorption by Na+ K+ ATPase inhibition. The reproducibility of the method was good. With a decrease of lithogenic bile index, the protective effect of alcohol against biliary cholesterol cholelithiasis could be due either to stimulation of gallbladder emptying and/or acceleration of gallbladder filling.