The effects of the dietary protein levels on liver lipids of the male rats were examined using 8, 20 and 32 % casein diets. Feeding a diet of 8 % casein resulted in considerably lower level of hepatic phospholipids in comparisons to that of 20 and 32 % casein. Modification of the fatty acid compositions of several lipid components tested was reflected in general by the levels of dietary casein. There was, however, no obvious differences in these parameters between 20 and 32 % casein diets. When comparisons were made between 8 and 32 % casein diets, ingestion of the lower dietary protein caused the decreased percentage of arachidonic acid and the increased percentage of palmitic and palmitoleic acids in lecithin. In triglyceride, the percentage of oleic acid was increased and that of linoleic acid decreased. The most remarkable change was noticed in the cholesterolester fraction in which almost all of the major components were altered by the levels of the dietary protein. These observations clearly indicated that the concentration and composition of each hepatic lipid component were specifically altered by the differences in the levels of dietary casein. Additionally, the dietary protein levels appeared to directly influence not only on the desaturation of linoleate to arachidonate but also on the pool size of these essential fatty acids. It is suggested that these alteration induced by differences in the dietary protein levels may influence the concentration of other fatty acids in the hepatic lipid components.