The inhibitory effect of dietary taurine on cholesterol gallstone formation was studied using male mice of Jcl:ICR strain. Mice were provided three kinds of semi-purified diet; a cholesterol-free diet (standard), a lithogenic diet containing 0.5% cholesterol and 0.25% sodium cholate (C-CA), and a lithogenic diet supplemented with 5% taurine. The changes of total cholesterol in serum, cholesterol mass in the liver and the gall bladder, and gallstone incidence were studied as a function of time. Gallstone formation was observed only in the mice fed on the C-CA diet for more than 3 weeks. The changes of serum cholesterol concentration were not consistent with gallstone formation. The cholesterol mass of the liver in taurine-supplemented mice decreased after the 3rd week. Cholesterol content of the gall bladder increased with cholesterol gallstone formation. Therefore, the inhibitory effect of dietary taurine on cholesterol gallstone formation may be related to the decrease in cholesterol content of the liver.