Abstract Lipid composition of liver in dogs was investigated after feeding them either an arteriosclerosis-inducing diet which contained 16% hydrogenated coconut oil and 5% cholesterol, the same diet but without cholesterol supplement, or meat-chow. Animals fed the last diet did not develop vascular lesions and were regarded as controls. The composition and concentration of free fatty acid and phospholipid fractions of hepatic lipids from dogs fed either experimental diet for 4 months were similar but differed from controls. However, cholesteryl oleate, total cholesteryl ester and triglyceride concentrations were significantly higher in liver of the group with cholesterol supplement than in the group without cholesterol added to their diet. In addition, the cholesterol supplemented diet fed for 12–16 months caused greater hepatic lipid changes than those induced by the same diet in 4 months. Unlike adipose tissue, kidney, or myocardial and skeletal muscle, hepatic cholesterol esters showed a profound difference between the four month feedings of cholesterol supplemented and cholesterol free diets. These findings suggest that the liver may play a predominant regulatory role in the onset of diet-induced hyperlipemia and that exogenous cholesterol enhances the effects seen by feeding saturated medium chain fatty acids without cholesterol. Lipid changes observed in mitochondrial and microsomal fractions generally were similar, and also like those observed in lipid extracts of whole liver.