The purpose of the study was to find an effect of Medium Chain Triglycerids (MCT) diet on cholesterol metabolism in rat. Sprague-Dawley rats were fed two different diets containing MCT(trioctanoate) and corn oil respectively. After feeding to each group for four weeks, the levels of serum and liver cholesterol, the excretion rates of fecal and biliary steroids, and also bile acid composition were investigated. The results obtained from the study are as follows : (1) The average body weight gain in MCT group was almost same as that in the corn oil group. (2) The concentration of serum cholesterol in MCT group was lower than that in the corn oil group. Therefore it is confirmed that the cholesterol lowing action of MCT diet was practically high. (3) The concentrations of liver cholesterol and Triglyceride in MCT group were almost same as that in the corn oil group. Therefore it is thought that the level of liver lipids was not influenced by the difference of diet in this study. (4) The excretion rate of fecal neutral steroid in MCT group was significantly lower than that in the corn oil group, while the rate of fecal bile acid excretion was about same in both MCT and corn oil group. (5) The composition rates of fecal bile acid such as cholic acid, chenodeoxycholic acid and deoxycholic acid, a secondary acid of cholic acid, in MCT group were significantly lower than that in the corn oil group. (6) The excretion rates of biliary cholesterol and bile acid in MCT group were significantly higher than that in the corn oil group, while the composition rates of biliary bile acid such as chenoddeoxycholic acid and deoxycholic acid in MCT group were significantly higher than that in the corn oil group.